Method of determining the driver selected operating mode of an automatic transmission system

ABSTRACT

A method of determining the driver selected operating mode of an automatic transmission system wherein a controller is programmed to determine the driver selected operating mode of the transmission with a binary code transmitted from sensors sensing the position of a manually actuated shift lever.

This is a continuation of U.S. patent application Ser. No. 07/189,553, filed Apr. 29, 1988, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automatic transmission primarily intended for motor vehicle use, and more particularly, to a method of determining the driver selected operating mode of a transmission that is controlled electronically and hydraulically.

2. Description Of Related Art

Generally speaking, land vehicles require three basic components. These components comprise a power plant (such as an internal combustion engine) a power train and wheels. The internal combustion engine produces force by the conversion of the chemical energy in a liquid fuel into the mechanical energy of motion (kinetic energy). The function of the power train is to transmit this resultant force to the wheels to provide movement of the vehicle.

The power train's main component is typically referred to as the "transmission". Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. The vehicle's transmission is also capable of controlling the direction of rotation being applied to the wheels, so that the vehicle may be driven both forward and backward.

A conventional transmission includes a hydrodynamic torque converter to transfer engine torque from the engine crankshaft to a rotatable input member of the transmission through fluid-flow forces. The transmission also includes frictional units which couple the rotating input member to one or more members of a planetary gearset. Other frictional units, typically referred to as brakes, hold members of the planetary gearset stationary during flow of power. These frictional units are usually brake clutch assemblies or band brakes. The drive clutch assemblies can couple the rotating input member of the transmission to the desired elements of the planetary gearsets, while the brakes hold elements of these gearsets stationary. Such transmission systems also typically provide for one or more planetary gearsets in order to provide various ratios of torque and to ensure that the available torque and the respective tractive power demand are matched to each other.

Transmissions are generally referred to as manually actuated or automatic transmissions. Manual transmissions generally include mechanical mechanisms for coupling rotating gears to produce different ratio outputs to the drive wheels.

Automatic transmissions are designed to take automatic control of the frictional units, gear ratio selection and gear shifting. A thorough description of general automatic transmission design principals may be found in "Fundamentals of Automatic Transmissions and Transaxles," Chrysler Corporation Training Manual No. TM-508A. Additional descriptions of automatic transmissions may be found in U.S. Pat. No. 3,631,744, entitled "Hydromatic Transmission," issued Jan. 4, 1972 to Blomquist, et al., and U.S. Pat. No. 4,289,048, entitled "Lock-up System for Torque Converter," issued on Sep. 15, 1981 to Mike, et al. Each of these patents is hereby incorporated by reference.

In general, the major components featured in such an automatic transmission are: a torque converter as above-mentioned; fluid pressure-operated multi-plate drive or brake clutches and/or brake bands which are connected to the individual elements of the planetary gearsets in order to perform gear shifts without interrupting the tractive power, one-way clutches in conjunction with the frictional units for optimization of power shifts; and transmission controls such as valves for applying and releasing elements to shift the gears (instant of shifting), for enabling power shifting, and for choosing the proper gear (shift point control), dependent on shift-program selection by the driver (selector lever), accelerator position, the engine condition and vehicle speed.

The control system of the automatic transmission is typically hydraulically operated through the use of several valves to direct and regulate the supply of pressure. This hydraulic pressure control will cause either the actuation or deactuating of the respective frictional units for effecting gear changes in the transmission. The valves used in the hydraulic control circuit typically comprise spring-biased spool valves, spring-biased accumulators and ball check valves. Since many of these valves rely upon springs to provide a predetermined amount of force, it will be appreciated that each transmission design represents a finely tuned arrangement of interdependent valve components. While this type of transmission control system has worked well over the years, it does have its limitations. For example, such hydraulically controlled transmissions are generally limited to one or a very small number of engines and vehicle designs. Therefore, considerable cost is incurred by an automobile manufacturer to design, test, build, inventory and repair several different transmission units in order to provide an acceptable broad model line for consumers.

Additionally, it should be appreciated that such hydraulically controlled transmission systems cannot readily adjust themselves in the field to compensate for varying conditions such as normal wear on the components, temperature swings and changes in engine performance over time. While each transmission is designed to operate most efficiently within certain specific intolerances, typical hydraulic control systems are incapable of taking self-corrective action on their own to maintain operation of the transmission at peak efficiency.

However, in recent years, a more advanced form of transmission control system has been proposed, which would offer the possibility of enabling the transmission to adapt itself to changing conditions. In this regard, U.S. Pat. No. 3,956,947, issued on May 18, 1976 to Leising, et al., which is hereby incorporated by reference, sets forth a fundamental development in this field. Specifically, this patent discloses an automatic transmission design which features an "adaptive" control system that includes electrically operated solenoid-actuated valves for controlling certain fluid pressures. In accordance with this electric/hydraulic control system, the automatic transmission would be "responsive" to an acceleration factor for controlling the output torque of the transmission during a shift from one ratio of rotation (between the input and output shafts of the transmission) to another. Specifically, the operation of the solenoid-actuated valves would cause a rotational speed versus time curve of a sensed rotational component of the transmission to substantially follow along a predetermined path during shifting.

3. Objects Of The Present Invention

It is one of the principal objects of the present invention to provide a significantly advanced electronically controlled transmission which is fully adaptive. By fully adaptive, it is means that substantially all shifts are made using closed-loop control (i.e., control based on feedback). In particular, the control is closed loop on speed, speed ratio, or slip speed of either N_(t) (turbine of the torque converter) and N_(e) (engine) or a combination of N_(t) and N_(o) (output) which will provide the speed ratio or slip speed. This transmission control is also capable of "learning" from past experience and making appropriate adjustments on that basis.

Another object of the present invention is to provide an automatic transmission in which the shift quality is maintained approximately uniform regardless of the engine size, within engine performance variations or component condition (i.e. the transmission control system will adapt to changes in engine performance or in the condition of the various frictional units of the transmission).

It is a more specific object of the present invention to provide a method of determining the driver selected operating mode such as park, reverse, neutral, overdrive, drive and low (PRNODDL) of the transmission.

This application is one of several applications filed on the same date, all commonly assigned and having similar Specifications and Drawings, these applications being identified below.

    ______________________________________                                         U.S. Ser. No.                                                                           Title                                                                 ______________________________________                                         187,772  AN ELECTRONICALLY-CONTROLLED,                                                  ADAPTIVE AUTOMATIC TRANSMISSION                                                SYSTEM                                                                187,751  AUTOMATIC FOUR-SPEED                                                           TRANSMISSION                                                          189,493  PUSH/PULL CLUTCH APPLY PISTON OF                                               AN AUTOMATIC TRANSMISSION                                             187,781  SHARED REACTION PLATES BETWEEN                                                 CLUTCH ASSEMBLIES IN AN AUTOMATIC                                              TRANSMISSION                                                          189,492  CLUTCH REACTION AND PRESSURE                                                   PLATES IN AN AUTOMATIC                                                         TRANSMISSION                                                          188,602  BLEEDER BALL CHECK VALVES IN AN                                                AUTOMATIC TRANSMISSION                                                188,610  PRESSURE BALANCED PISTONS IN AN                                                AUTOMATIC TRANSMISSION                                                189,494  DOUBLE-ACTING SPRING IN AN                                                     AUTOMATIC TRANSMISSION                                                188,613  PARK LOCKING MECHANISM FOR AN                                                  AUTOMATIC TRANSMISSION                                                187,770  SOLENOID-ACTUATED VALVE                                                        ARRANGEMENT OF AN AUTOMATIC                                                    TRANSMISSION SYSTEM                                                   188,796  RECIPROCATING VALVES IN A FLUID                                                SYSTEM OF AN AUTOMATIC                                                         TRANSMISSION                                                          187,705  VENT RESERVOIR IN A FLUID SYSTEM                                               OF AN AUTOMATIC TRANSMISSION                                          188,592  FLUID ACTUATED SWITCH VALVE IN AN                                              AUTOMATIC TRANSMISSION                                                188,598  DIRECT-ACTING, NON-CLOSE                                                       CLEARANCE SOLENOID-ACTUATED                                                    VALVES                                                                188,618  NOISE CONTROL DEVICE FOR A                                                     SOLENOID-ACTUATED VALVE                                               188,605  FLUID ACTUATED PRESSURE SWITCH                                                 FOR AN AUTOMATIC TRANSMISSION                                         187,210  METHOD OF APPLYING REVERSE                                                     GEAR OF AN AUTOMATIC TRANSMISSION                                     187,672  TORQUE CONVERTER CONTROL VALVE                                                 IN A FLUID SYSTEM OF AN AUTOMATIC                                              TRANSMISSION                                                          187,120  CAM-CONTROLLED MANUAL VALVE IN                                                 AN AUTOMATIC TRANSMISSION                                             187,181  FLUID SWITCHING MANUALLY                                                       BETWEEN VALVES IN AN                                                           AUTOMATIC TRANSMISSION                                                187,704  METHOD OF OPERATING AN                                                         ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,020  METHOD OF SHIFT SELECTION IN AN                                                ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   187,991  METHOD OF UNIVERSALLY                                                          ORGANIZING SHIFTS FOR AN                                                       ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,603  METHOD OF DETERMINING AND                                                      CONTROLLING THE LOCK-UP OF                                                     A TORQUE CONVERTER IN AN                                                       ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,617  METHOD OF ADAPTIVELY IDLING AN                                                 ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,615  METHOD OF DETERMINING THE                                                      SHIFT LEVER POSITION OF                                                        AN ELECTRONIC AUTOMATIC                                                        TRANSMISSION SYSTEM                                                   188,594  METHOD OF DETERMINING THE                                                      ACCELERATION OF A TURBINE                                                      IN AN AUTOMATIC TRANSMISSION                                          187,771  METHOD OF DETERMINING THE                                                      FLUID TEMPERATURE OF AN                                                        ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,607  METHOD OF DETERMINING THE                                                      CONTINUITY OF SOLENOIDS IN AN                                                  ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   189,579  METHOD OF DETERMINING THE                                                      THROTTLE ANGLE POSITION FOR AN                                                 ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,604  METHOD OF CONTROLLING THE                                                      SPEED CHANGE OF A KICKDOWN SHIFT                                               FOR AN ELECTRONIC AUTOMATIC                                                    TRANSMISSION SYSTEM                                                   188,591  METHOD OF CONTROLLING THE                                                      APPLY ELEMENT DURING A KICKDOWN                                                SHIFT FOR ELECTRONIC                                                           AUTOMATIC TRANSMISSION SYSTEM                                         188,608  METHOD OF CALCULATING TORQUE                                                   FOR AN ELECTRONIC AUTOMATIC                                                    TRANSMISSION SYSTEM                                                   187,150  METHOD OF LEARNING FOR                                                         ADAPTIVELY CONTROLLING AN                                                      ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,595  METHOD OF ACCUMULATOR CONTROL                                                  FOR A FRICTION ELEMENT IN AN                                                   ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,599  METHOD OF ADAPTIVELY                                                           SCHEDULING A SHIFT FOR AN                                                      ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,601  METHOD OF SHIFT CONTROL DURING                                                 A COASTDOWN SHIFT FOR AN                                                       ELECTRONIC AUTOMATIC                                                           TRANSMISSION SYSTEM                                                   188,620  METHOD OF TORQUE PHASE                                                         SHIFT CONTROL FOR AN ELECTRONIC                                                AUTOMATIC TRANSMISSION                                                188,596  METHOD OF DIAGNOSTIC                                                           PROTECTION FOR AN ELECTRONIC                                                   AUTOMATIC TRANSMISSION SYSTEM                                         188,597  METHOD OF STALL TORQUE                                                         MANAGEMENT FOR AN ELECTRONIC                                                   AUTOMATIC TRANSMISSION SYSTEM                                         188,606  METHOD OF SHIFT TORQUE                                                         MANAGEMENT FOR AN ELECTRONIC                                                   AUTOMATIC TRANSMISSION SYSTEM                                         188,616  ELECTRONIC CONTROLLER FOR AN                                                   AUTOMATIC TRANSMISSION                                                188,600  DUAL REGULATOR FOR REDUCING                                                    SYSTEM CURRENT DURING AT                                                       LEAST ONE MODE OF OPERATION                                           188,619  UTILIZATION OF A RESET                                                         OUTPUT OF A REGULATOR                                                          AS A SYSTEM LOW-VOLTAGE INHIBIT                                       188,593  THE USE OF DIODES IN AN                                                        INPUT CIRCUIT TO TAKE                                                          ADVANTAGE OF AN ACTIVE PULL-DOWN                                               NETWORK PROVIDED IN A DUAL                                                     REGULATOR                                                             188,609  SHUTDOWN RELAY DRIVER CIRCUIT                                         188,614  CIRCUIT FOR DETERMINING                                                        THE CRANK POSITION OF AN                                                       IGNITION SWITCH BY SENSING                                                     THE VOLTAGE ACROSS THE STARTER                                                 RELAY CONTROL AND HOLDING                                                      AN ELECTRONIC DEVICE IN A                                                      RESET CONDITION IN RESPONSE                                                    THERETO                                                               188,612  THROTTLE POSITION SENSOR                                                       DATA SHARED BETWEEN CONTROLLER                                                 WITH DISSIMILAR GROUNDS                                               188,611  NEUTRAL START SWITCH TO                                                        SENSE SHIFT LEVER POSITION                                            188,981  OPEN LOOP CONTROL OF SOLENOID                                                  COIL DRIVER                                                           ______________________________________                                           "Commonly assigned application Ser. No. 07/187,772, filed Apr. 29, 1988      now U.S. Pat. No. 4,875,391 will be printed in its entirety. The Figures      and the entire Specification of that application are specifically      incorporated by reference. For a description of the above copending      applications, reference is made to the above mentioned U.S. Pat. No.      4,875,391."

SUMMARY OF THE INVENTION

To achieve the foregoing objects, the present invention provides a comprehensive four-speed automatic transmission system. While this transmission system particularly features a fully adaptive electronic control system, numerous other important advances are incorporated into this unique transmission system, as will be described below in detail.

The transmission control system includes a microcomputer-based controller which receives input signals indicative of parameters such as engine speed, turbine speed, output speed (vehicle speed), throttle angle position, brake application, predetermined hydraulic pressure, the driver selected gear or operating condition (PRNODDL), engine coolant temperature, and/or ambient temperature. This controller generates command or control signals for causing the actuation of a plurality of solenoid-actuated valves which regulate the application and release of pressure to and from the frictional units of the transmission system. Accordingly, the controller will execute predetermined shift schedules stored in the memory of the controller through appropriate command signals to the solenoid-actuated valves and the feedback which is provided by various input signals.

In accordance with one aspect of the present invention, the controller is programmed to determine the driver selected operating mode (PRNODDL) of the transmission with a binary code transmitted from sensors sensing the position of the manually actuated shift lever.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims and in the accompanying drawings in which:

FIGS. 1A-E illustrate one physical embodiment of the transmission according to the present invention;

FIG. 1A is a perspective view, partially broken away of the transmission;

FIG. 1B is a sectional elevational view of one embodiment of a transmission constructed according to the present invention;

FIG. 1C is a partial sectional elevational view of one half of the transmission of FIG. 1B;

FIG. 1D is a partial sectional elevational view of the other half of the transmission of FIG. 1B; and

FIG. 1E is a schematic diagram of the transmission of FIGS. 1A and 1B;

FIG. 2 is a fragmentary view of the park locking mechanism according to the present invention;

FIGS. 3A-L are schematic diagrams of the hydraulic circuits employed in the transmission according to the present invention in various gear positions;

FIG. 4 is a flow chart of the overall operational methodology of the transmission controller according to the present invention;

FIGS. 5A-D illustrate the shift schedule methodology according to the present invention;

FIG. 5A is a flow chart of the shift schedule methodology of FIG. 4; and

FIGS. 5B-5D are shift schedule graphs;

FIGS. 6A-6B illustrate the PSLOPE methodology according to the present invention;

FIG. 6A is a flow chart of the PSLOPE methodology of FIGS. 5; and

FIG. 6B is a graph of the method used in FIG. 6A;

FIG. 7 is a schematic diagram of the PRNODDL methodology of FIG. 4 according to the present invention;

FIGS. 8A and 8B are flow charts of the shift lever position methodology according to the present invention;

FIG. 9 is a block diagram of an adaptive control system for an automatic transmission according to the present invention;

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1A and 1B, an automatic transmission 100 according to one embodiment of the present invention is shown. The transmission 100 is adapted to be used in a vehicle (not shown), such as an automobile. However, it should be appreciated that the principles of the present invention may be employed in other types of vehicles and devices. The transmission 100 includes a transmission housing or case 102 for enclosing the numerous subassemblies which make up the transmission 100, including a torque converter assembly 110, pump assembly 200, multi-clutch assembly 300 and gear assembly 500.

TORQUE CONVERTER ASSEMBLY STRUCTURE

The torque converter assembly 110 is operative to transmit power from a rotating crankshaft 114 of a prime mover such as an automobile engine (not shown) to the input member of the transmission 100. This power may then be subsequently transmitted to a drive unit 104 (partially shown) which is connected to one or more drive wheels (not shown) of the vehicle. The torque converter 110 is generally comprised of an impeller assembly 126, turbine assembly 128 and a stator assembly 130.

As illustrated in FIG. 1C, power is transmitted from the rotating crankshaft 114 of the engine to a front cover member 116 of the impeller assembly 126 through a rotatable plate member 118. Balance weights 119 are circumferentially spaced about the outer periphery of the front cover member 116. The plate member 118 is secured proximate its inner periphery to the crankshaft 114 by suitable fastening means such as bolts 120, and is likewise secured proximate its outer periphery to the front cover member 116 by suitable fastening means such as bolts 122. The front cover member 116 is secured, such as by welding at 124, to the impeller assembly 126 of the torque converter 110.

The impeller assembly 126 is fluidly connected in toroidal flow relationship in a known manner with the turbine assembly 128 and the stator assembly 130. The impeller assembly 126 comprises a plurality of circumferentially spaced impeller blades 132 connected to the inside of an impeller shell 134. The impeller shell 134 is secured, such as by welding at 136, to an impeller hub or pump drive shaft 138. The impeller hub 138 is drivingly engaged at its neck portion 140 to the positive displacement pump 200, from which fluid is supplied to the torque converter 110 in a manner to be described herein. An arcuate inner portion 142 of the impeller blade 132 is disposed about one half of a split torus ring 144 which reduces fluid turbulence within the torque converter 110. A thrust plate 146 is connected by tabs (not shown) on the inner surface of a slot 148 of the impeller hub 138 and disposed between the impeller assembly 126 and a stator thrust member 165.

The stator assembly 130 includes a plurality of circumferentially spaced stator vanes 150 which are connected at their inner end to a stator plate 152. The stator plate 152 is mounted on a one-way or over-running clutch assembly, generally indicated at 154. The over-running clutch assembly 154 permits rotation only in the direction of the impeller assembly 126. The over-running clutch assembly 154 comprises an over-running clutch cam 156 mounted about over-running clutch rollers 158, which in turn, travel about an over-running clutch race 160. The over-running clutch race 160 is splined at inner surface 162 to a stationary reaction shaft member 164. An annular thrust member 165 having retaining transverse flanges or tabs 167 is disposed between the stator plate 152 and the thrust plate 146.

The turbine assembly 128 includes a plurality of circumferentially spaced turbine blades 166 which are connected to the inside of a turbine shell 168. The turbine shell 168 is secured by rivets 170 or the like to a turbine hub member 172. The turbine hub member 172 is drivingly connected, as by a spline connection 174, to a rotatable input member or shaft 176 to which the gear assembly 500 of the transmission 100 is drivingly engaged. A turbine hub seal 178 is disposed between the inside of the turbine hub member 172 and the input shaft 176 to prevent entry of fluid therebetween. A cover bushing 180 having grooves (not shown) for fluid flow therethrough supports the turbine hub member 172 in a cavity 182 of the front cover member 116. A thrust plate or washer 184 having grooves (not shown) for fluid flow therethrough is disposed between the turbine hub member 172 and the front cover member 116. An annular stepped member 185 having grooves (not shown) for fluid flow therethrough is disposed between the turbine hub member 172 and stator plate 152, as well as the over-running clutch race 160.

The torque converter 110 also includes a lock-up clutch assembly, generally indicated at 186, to prevent slip between the rotating crankshaft 114 of the engine and the turbine assembly 128 of the torque converter 110. The lock-up clutch assembly 186 includes an annular piston member 188 having an inner flange portion 190 disposed about the turbine hub member 172 of the turbine assembly 128. The piston member 188 has a plurality of circumferentially spaced inverted U-shaped outer flange portions 192 which are formed to engage corresponding slots 194 in a drive ring 196 that is welded to the turbine shell 168. The piston member 188 is slidingly and sealingly mounted for axial movement on the outer axial surface of the turbine hub member 172 through annular seal element 198. An annular disc-shaped frictional element or lock-up disc 199 is carried proximate the outer periphery of the front cover member 116 for engagement with a cooperating portion of the piston member 188.

PUMP ASSEMBLY STRUCTURE

The fixed positive displacement pump assembly 200 includes a pump housing 202 secured proximate its inner periphery to a reaction shaft support 204 by suitable fastening means such as bolts 206. The pump housing 202 is likewise secured proximate its outer periphery to the transmission case 102 by suitable fastening means such as bolts 208. The reaction shaft support 204 is secured, such as by press fitting with splines at 210, to the reaction shaft member 164. The impeller hub or pump drive shaft 138 is supported in the pump housing 202 through a bushing member 212 A seal ring assembly 214 is disposed about the impeller hub or pump drive shaft 138 in a bore or recess 216 at one end of the pump housing 202 to prevent fluid from exiting the end of the pump housing 202. An outer gear or rotor 218 with internal teeth (not shown) operates within a bore 220 of the pump housing 202. An inner gear or rotor 222 having external teeth (not shown), cooperative with the teeth of the outer rotor 218, is disposed within the outer rotor 218. As illustrated in FIGS. 1C and 1D, sealing means, such as seal rings 224, 226 and 228, are axially spaced between the input shaft 176 and reaction shaft support 204. The reaction shaft support 204 includes a fluid passage 230 to allow fluid to flow to the torque converter 110 in a manner to described herein.

MULTI-CLUTCH ASSEMBLY STRUCTURE

During the flow of power through the transmission 100, the multi-clutch assembly 300 provides a means for application and release of two separate members to and from each other. In other words, the multi-clutch assembly 300 is the means by which the gears within the transmission are selectively engaged and disengaged from either the crankshaft 114 of the prime mover or the transmission case 102. Near the input side of the transmission 100, the multi-clutch assembly 300 includes an underdrive clutch 302 (applied in first, second and third gears), overdrive clutch 304 (applied in third and fourth gears) and a reverse clutch 306 (applied in reverse gear) assemblies. Near the output side of the transmission 100, the multi-clutch assembly 300 includes a two/four shift clutch assembly 308 (applied in second and fourth gears), and a low/reverse clutch assembly 310 (applied in first and reverse gears).

As illustrated in FIGS. 1C and 1D, an input clutch retainer hub 312 is provided to house the input clutch assemblies 302, 304 and 306. The input clutch retainer hub 312 has a generally axially extending shoulder portion 313 and a generally axially extending portion 314. A plurality of spaced seal rings 315 are disposed in corresponding annular grooves 316 which are formed along the reaction shaft support 204. The input clutch retainer hub 312 is also splined at 317 to the input shaft 176. A thrust bearing 318 is disposed axially between one end of the reaction shaft support 204 and the axially extending portion 314 of the input clutch retainer hub 312. The input clutch retainer hub 312 has teeth 319 at its outer periphery. A turbine speed sensor 320 threadably engages a bore 322 in the transmission case 102 and has one end 324 disposed or spaced radially just above the teeth 319 of the input clutch retainer hub 312. The turbine speed sensor 320 is used to monitor or sense the revolution rate of the turbine assembly 128 by counting the teeth 319 passing thereby in relation to time. Preferably, a passive type speed sensor is used for the turbine speed sensor 320. An input clutch retainer 326 has a hub portion 328 disposed about and drivingly connected to, as by a spline connection 330, to the axially extending portion 314 of the input clutch retainer hub 312. Sealing means, such as sealing rings 332 and 334, are disposed in corresponding grooves of the input clutch hub retainer 312 between the hub portion 328 and the axially extending portion 314 of the input clutch retainer hub 312. A tapered snap ring 336 is disposed in a groove 338 of the input clutch retainer hub 312 to prevent axial movement of the input clutch retainer 326 toward the gear assembly 500. The input clutch retainer 326 includes an axially extending flange 340 forming a cylinder. A plurality of circumferentially spaced clutch retainer fingers 341 extend radially inwardly from the flange 340 to which the clutch plates, which will be described herein, are mounted.

As illustrated in FIG. 1D, the underdrive clutch assembly 302 comprises a plurality of axially spaced annular clutch plates 342 and a plurality of axially spaced annular clutch discs 344. The clutch discs 344 are alternated between the clutch plates 342 and when the clutch assembly 302 is not applied, these plates and discs are free to move or rotate relative to each other. The clutch plates 342 have splines (not shown) on their outer diameter and mount in grooves 346 of the clutch retainer fingers 341 which are inside the input clutch retainer 326. The clutch discs 344 have internal splines (not shown) and are lined with a friction material 347. The clutch discs 344 are mounted in grooves 348 in an underdrive clutch hub 350. The underdrive clutch hub 350 is integral with a rotatable underdrive gear shaft 352 of the gear assembly 500. A thrust bearing 353 is disposed axially between the axially extending portion 31 of the input clutch retainer hub 312 and underdrive clutch hub 350.

The overdrive clutch assembly 304 comprises a plurality of axially spaced annular clutch plates 354 and a plurality of axially spaced annular clutch discs 356. The clutch plates 354 and clutch discs 356 are similar to those of the underdrive clutch assembly 302. Clutch discs 356 are disposed in splines formed in an overdrive clutch hub 358 which is supported by bushings 360 and 361 about the gear shaft 352. Thrust members 362 and 363 are disposed axially between the underdrive clutch hub 350 and overdrive clutch hub 358. The thrust members 362 and 363 are similar to the thrust member 165. An annular reaction plate 36 is secured to the inside of the input clutch retainer 326 axially between the underdrive and overdrive clutch plates and discs 342, 344 354 and 356, respectively. The reaction plate 36 is shared by the underdrive 302 and overdrive 304 clutch assemblies. Annular snap rings 366 and 368 are disposed on the sides of the reaction plate 364. Snap ring 368 is a tapered ring, restraining reaction plate 364 from axial movement.

The reverse clutch assembly 306 comprises at least one annular clutch plate 370 and a plurality of axially spaced annular clutch discs 372. The reverse clutch plate 370 and clutch discs 372 are similar to those of the underdrive clutch assembly 302. The reverse clutch discs 372 are mounted in splines 373 of a reverse clutch hub 374. The reverse clutch hub 374 is supported by bushings 376 and 378 about one end of the overdrive clutch hub 358. A thrust member 379 is disposed axially between the overdrive clutch hub 358 and reverse clutch hub 379. The thrust member 379 is similar to the thrust member 165. An annular reaction plate 380 is mounted about one end of the flange 340 of the input clutch retainer 326 on one side of the reverse clutch plate 370 and discs 372. Selective snap rings 384 secure the reaction plate 380 from axial movement along the input clutch retainer 326.

To apply the overdrive clutch assembly 304 and reverse clutch assembly 306, a fluid actuating device such as a first hydraulic piston 386 has an axially extending projection 388 which operates in a bore or recess 390 of the input clutch retainer hub 312. The inner diameter of the projection 388 has a groove 392 provided for a snap ring 394, while the recess 390 of the input clutch retainer hub 312 has a groove 396 for a sealing means such as a synthetic rubber seal ring 398. The first hydraulic piston 386 is slidingly and sealingly mounted for axial movement on the outer diameter of the hub portion 328 of the input clutch retainer 326 through sealing means 400 at its inner periphery and near the outer periphery of the input clutch retainer 326 through sealing means 402. A double-acting spring means such as a Belleville like spring 404 is disposed between the first hydraulic piston 386 and the input clutch retainer hub 312 to bias or return the first hydraulic piston 386 to its non-displaced or non-applied position shown in the figure. The double-acting spring 404 has a conical shape with fingers 405 and is formed with a linear slope such that its inner and outer diameters do not lie in the same cross-sectional plane. The double-acting spring 404 will be discussed more in detail under the section heading "DOUBLE-ACTING SPRING".

The first hydraulic piston 386 includes an axially extending cylinder portion 406 which has an annular pressure plate member 408 secured at one end thereof by waved snap ring 409a and snap ring 409b. A pressure plate member 408 is interposed between the overdrive clutch assembly 304 and the reverse clutch assembly 306 to engage the clutch plates 354, 370 and discs 356, 372, respectively. Hence, the single pressure plate member 408 is shared by the overdrive clutch 304 and reverse clutch 306 assemblies.

To engage or disengage the underdrive clutch assembly 302, a second hydraulic piston 410 operates in a recess 412 of the input clutch retainer 326. The smooth outer diameter of the hub portion 314 of the input clutch retainer hub 312 has a groove 414 provided with a sealing means such as a synthetic rubber inner seal ring 416, while the outer periphery of recess 412 has a groove 418 for an outer seal ring 420. The second hydraulic piston 410 has one end 422 abutting the clutch plates 342 of the underdrive clutch assembly 302. An annular conically shaped spring retainer member 424 is abuttingly mounted against a snap ring 426. The snap ring 426 is disposed in a groove 428 formed in the axially extending portion 314 of the input clutch retainer hub 312. The other end of the spring retainer member 424 is in sealing engagement with the second hydraulic piston 410 through sealing means 430. The spring retainer member 424 is filled with fluid fed through an orifice (not shown) in the second hydraulic piston 410 from a passage (not shown) in the input clutch retainer hub 312 to provide the pressure balance for the second hydraulic piston 410. The excess fluid is allowed to leak past the snap ring 426 to cool the underdrive clutch assembly 302. A spring means such as a coiled spring 432 is disposed between the spring retainer member 424 and the second hydraulic piston 410 to bias or return the second hydraulic piston 410 to its original position shown in the figure when not applied.

At the output end of the transmission 100, the transmission case 102 houses the output or brake clutch assemblies such as the two/four shift clutch assembly 308 and the low/reverse clutch assembly 310. The two/four shift clutch assembly 308 comprises a plurality of axially spaced annular clutch plates 434 and a plurality of axially spaced annular clutch discs 436. The clutch plates 434 and clutch discs 436 are similar to those of the underdrive clutch assembly 302. The clutch plates 434 are mounted in splines 438 of circumferentially spaced and radially inwardly extending case clutch fingers 439 inside the transmission case 102. The clutch discs 436 are mounted in splines 440 formed in an axially extending flange 442 of the reverse clutch hub 374. A spring means such as a Belleville like spring 444, similar to spring 404, is mounted inside the transmission case 102 on one side of the two/four shift clutch assembly 308. An annular reaction plate 445 is mounted on the other side of the two/four shift clutch assembly 308 and between the two/four shift clutch assembly 308 and the low/reverse clutch assembly 310. The reaction plate 445 is shared by the two/four shift clutch 308 and low/reverse clutch 310 assemblies. Snap rings 446 and 447 are mounted in the transmission case 102 on the sides of the reaction plate 445 to lock it in place. Snap ring 446 is a tapered ring, restraining reaction plate 445 from axial movement.

To apply the two/four shift clutch assembly 308, a third hydraulic piston 448 operates in a cavity 450 formed by an annular piston housing 452. The piston housing 452 is secured to the transmission case 102 by suitable fastening means (not shown). The smooth diameter of the third hydraulic piston 448 has a groove 454 formed in its outer periphery for an outer seal ring 456 and a groove 458 formed in its inner periphery for an inner seal ring 460. A snap ring 462 is disposed in a groove 464 in the transmission case 102 to prevent axial movement of the piston housing 452.

The low/reverse clutch assembly 310 comprises a plurality of axially spaced annular clutch plates 466 and a plurality of axially spaced annular clutch discs 468. The clutch plates 466 and clutch discs 468 are similar to those of the underdrive clutch assembly 302. The clutch plates 466 are mounted in splines 470 of the case clutch fingers 439 inside the transmission case 102. The clutch discs 468 are mounted in splines 472 of the outer periphery of an annulus gear 542 of the gear assembly 500 to be described further herein.

To apply the low/reverse clutch assembly 310, a fourth hydraulic piston 474 operates in a cavity 476 formed by an annular piston housing 478. The piston housing 478 is disposed in an annular recess 480 of the transmission case 102 and secured by suitable fastening means, such as bolts 481, to the transmission case 102. The smooth diameter of the fourth hydraulic piston 474 has a groove 482 formed in its outer periphery for an outer seal ring 484 and a groove 486 formed in its inner periphery for an inner seal ring 488. A spring means such as a Belleville like spring 490, similar to spring 404, is disposed between the fourth hydraulic piston 474 and the gear assembly 500 to bias or return the fourth hydraulic piston 474 to its original position when not applied as shown in the figure. A snap ring 492 retains one end of the spring 490 to the transmission case 102.

GEAR ASSEMBLY STRUCTURE

During the flow of power, the gear assembly 500 changes the ratio of torque between an input member, such as input shaft 176, and an output member, such as output gear 534 which will be further described herein. The gear assembly 500 comprises a front or first planetary gear set, generally indicated at 502, and an axially spaced rear or second planetary gear set, generally indicated at 504. The first planetary gear set 502 includes a first sun gear 506 at its center. The first sun gear 506 is connected to the reverse clutch hub 374 at its inner periphery and is supported upon bushings 376 and 378. A first planet carrier 508 is disposed about the first sun gear 506. The first planet carrier 508 includes a plurality of circumferentially spaced first pinion gears 510 mounted about shafts 512 connected to the first planet carrier 508. The first planet carrier 508 includes an inner portion 514 splined at 516 to the overdrive clutch hub 358. A thrust bearing 517 is disposed axially between one end of the first sun gear 506 and inner portion 514 of the first planet carrier 508. The first planet carrier 508 also includes an axially extending outer portion 518 forming a cylinder about the first planetary gear set 502. A first annulus gear 519 is disposed about the first planet carrier 508 and engages the first pinion gears 510.

The rear or second planetary gear set 504 includes a second sun gear 520 at its center which is splined at 522 to the gear shaft 352. A thrust bearing 523 is axially disposed between one end of the inner portion 514 of the first planet carrier 508 and the second sun gear 520. A second planet carrier 524 is disposed about the second sun gear 520. The second planet carrier 524 includes a plurality of circumferentially spaced second pinion gears 526 mounted about shafts 528 connected to the second planet carrier 524. The second planet carrier 524 includes an inner portion 530 splined at 532 to a rotatable output gear 534 which acts as the output member of the transmission 100. The inner portion 530 of the second planet carrier 524 is supported by a bushing 536 disposed about the second sun gear 520. A thrust bearing 537 is disposed axially between the second sun gear 520 and second planet carrier 524. A tapered roller bearing assembly 538 supports the inner portion 530 of the second planet carrier 524 within the transmission case 102.

The second planet carrier 524 also includes an outer portion 540 connected to the first annulus gear 519. The second annulus gear 542 is disposed about the second planet carrier 524 and engages the second pinion gears 526. The second annulus gear 542 is connected to the outer portion 518 of the first planet carrier 508.

The second planet carrier 524 includes teeth 544 at its outer periphery of the outer portion 540. An output speed sensor 546 threadably engages a bore 548 in the transmission case 102 and has one end 550 disposed or radially spaced just above the teeth 544 of the second planet carrier 524. The output speed sensor 546 is used to monitor or sense the revolution rate (per minute) of the second planet carrier 524 by counting or sensing the teeth 544 passing thereby relative to time. The output speed sensor 546 is similar to the turbine speed sensor 320. It should also be noted that other suitable speed sensors could be used inside or after the transmission 100 to provide an output speed signal to the transmission's controller 3010.

The output gear 534 is secured to the second planet carrier 524 by suitable fastening means such as a bolt 552. The output gear 534 is supported by a tapered roller bearing assembly 554 within the transmission case 102. A rear cover plate member 556 is connected by suitable fastening means (not shown) to the rear or output end of the transmission case 102 to enclose the output gear 534 and the transfer gear (not shown).

To visualize and understand how power is transmitted from the rotating crankshaft 114 of the engine to the output gear 534 of the transmission 100, the operation of the assemblies described above will now be discussed in connection with FIGS. 1C, 1D and 1E.

OPERATION OF THE TORQUE CONVERTER

Rotation of the crankshaft 114 of the engine causes the front cover member 116 to rotate with it due to the connection between bolts 120, plate member 118 and bolts 122. Since the front cover member 116 is welded at 124 to the impeller shell 134 of the impeller assembly 126, the impeller assembly 126 also rotates with the crankshaft 114. The fluid within the impeller assembly 126 is set into motion by the rotation of the impeller assembly 126 and by the fluid pressure from the pump assembly 200. The impeller blades 132 start to carry the fluid around with them. As the fluid is spun around by the impeller blades 132, it is thrown outward by centrifugal force and into the turbine assembly 128 at an angle. The fluid strikes the turbine blades 166 of the turbine assembly 128, thus imparting torque, or turning effort to the turbine assembly 128 and causing the turbine shell 168 and the turbine assembly 128 to rotate. Since the turbine shell 168 is connected to the turbine hub 172 through rivets 170 and the turbine hub 172 is splined at 174 to the input shaft 176, the input shaft 176 is caused to rotate. As engine speed is increased, the force of the fluid striking the turbine blades 166 is also increased. Thus, torque is imparted to the input shaft 176 of the transmission 100 via the turbine assembly 128.

In the torque converter 110, the stator assembly 130 redirects the fluid flow so that the turbine blades 166 will have more force exerted upon them during a torque multiplication stage. During torque multiplication, the over-running clutch assembly 154 in the stator assembly 130 is locked in a known manner so that the stator assembly 130 will remain stationary. As the fluid passes from the turbine assembly 128 to the impeller assembly 126, the stator blades 150 of the stator assembly 130 "push" the fluid against the impeller blades 132 so that a greater entry angle is imparted to the turbine blades 166, resulting in a greater force on the blades 166 and increasing the torque to the input shaft 176 of the transmission 100.

The over-running clutch assembly 154 also permits the stator assembly 130 to rotate only in the same direction as the impeller assembly 126. The over-running clutch assembly 154 resists torque in one direction for the purpose of making the stator plate 152 and stator vanes 150 stationary. This is accomplished by the clutch rollers 158 engaging radially narrowing recesses (not shown) in the over-running clutch cam 156 to cause the over-running clutch cam 156, rollers 158 and race 160 to form a single unit. Since the over-running clutch race 160 is splined at 162 to the reaction shaft 164 which, in turn, is welded at 210 to the reaction shaft support 204 which cannot rotate, the over-running clutch cam 156, rollers 158 and race 160 remain stationary, resulting in the stator plate 152 and vanes 150 remaining stationary. The over-running clutch assembly 154 allows the stator plate 152 and vanes 150 to rotate freely in the opposite direction when their function as a reaction member is not desired because the rollers 158 do not engage the recesses, resulting in the over-running clutch cam 156 rotating freely about the clutch race 160.

OPERATION OF TORQUE CONVERTER LOCK-UP

The lock-up function of the torque converter 110 will now be described. Fluid flows through the center passage 175 of the input shaft 176 into the cavity 182 of the front cover member 116. The turbine hub seal 178 prevents leakage of the fluid back around the input shaft 176. The fluid in cavity 182 flows through slots (not shown) in the front cover bushing 180 and the thrust washer 184 and against the lock-up piston 188. The fluid pushes the portion 192 of the lock-up piston 188 off the friction disc 199, resulting in non-lock-up operation. At the same time, fluid from the pump assembly 200 flows through passage 230 in the reaction shaft support 204 and between the input shaft 176 and reaction shaft member 164. This fluid flows through slots (not shown) in the stepped member 185 and into the turbine 128, stator 130 and impeller 126 assemblies of the torque converter 110. Fluid also flows from these assemblies 126, 128 and 130 between the lock-up piston 188 and the turbine shell 168. Hence, during normal torque converter operation, fluid flow is acting on the opposite side of the lock-up piston 188, attempting to apply the lock-up piston 188. When the input shaft fluid is vented, the torque converter fluid pushes the lock-up piston 188 against the front cover member 116 with the friction disc 199 sandwiched between the two elements. Engine torque can then go through the front cover member 116 to the lock-up piston 188 and, in turn, to drive ring 196 and turbine shell 168.

As will be appreciated, lock-up of the torque converter 110 is desirable to reduce or eliminate rotational speed difference or "slip" between the crankshaft 114 of the engine and the input shaft 176 of the transmission 100. Lock-up of the torque converter 110 may be partial or full lockup. Partial lockup will reduce slip to predetermined value. Full lockup will eliminate slip or reduce it to a zero value. Lockup of the torque converter 110 may occur in second, third and fourth gears.

OPERATION OF PUMP

The general operation of the pump assembly 200 will now be described. Specific fluid flow from the pump 200 to various assemblies in the transmission 100 will be described in other sections herein.

The pump 200 creates flow and applies force to the fluid. As described previously, the impeller shell 134 is welded at 136 to the impeller hub 138 which acts as the pump drive shaft of the pump assembly 200. Rotation of the impeller shell 134 results in rotation of the impeller hub 138. Thus, the external source of power for the pump 200 is the engine.

In the pump assembly 200, both rotor members 218 and 222 rotate together. The inner rotor 222 is splined at 140 to the impeller hub 138 and, therefore, rotates as the impeller hub 138 rotates. As the inner rotor 222 rotates or drives the outer rotor 218, a space (not shown) between the rotors 218, 222 increases as the rotor teeth separate and pass an outlet port (not shown).

In the pump assembly 200, a crescent-shaped protrusion (not shown) of the pump housing 202 divides the rotors 218 and 222. Fluid is trapped between the protrusion and the rotor teeth as it is carried to the outlet port for further use in a manner to be described in other sections herein.

OPERATION OF THE CLUTCHES

As described previously, the input shaft 176 of the transmission 100 is rotating due to torque being transferred from the rotating crankshaft 114 of the engine and through the torque converter 110 to the input shaft 176. The input clutch retainer hub 312 also rotates with the input shaft 176 due to its spline connection 317 with the input shaft 176. The input clutch retainer 326 and clutch plates 342, 354 and 370 also rotate with the input shaft 176 due to the spline connection 330 of the input clutch retainer 326 to the input clutch retainer hub 312 and spline connection of clutch plates 342, 354 and 370 to the input clutch retainer 326.

To apply the underdrive clutch assembly 308, hydraulic pressure from fluid entering between the input clutch retainer 326 and second hydraulic piston 410 moves the second hydraulic piston 410 axially, thereby compressing the spring 432. The second hydraulic piston 410 forces the rotating clutch plates 342 and momentarily stationary discs 344 of the underdrive clutch assembly 302 together and produces frictional force between the clutch plates 342 and discs 344. Because the input clutch retainer 326 and underdrive clutch plates 342 are rotating, the frictional force causes the underdrive clutch discs 344 and hub 350 to rotate, in turn, rotating gear shaft 352 of the gear assembly 500. When the hydraulic fluid to the underdrive clutch assembly 302 is vented, the compressed spring 432 applies a force to the second hydraulic piston 410, thereby returning the second hydraulic piston 410 to its non-applied position as shown in the figure.

To apply the overdrive clutch assembly 304, hydraulic pressure from fluid entering between the first hydraulic piston 386 and the input clutch retainer 326 moves or pulls the first hydraulic piston 386 axially, thereby deflecting axially the spring 404. The pressure plate member 408 of the first hydraulic piston 386 forces the clutch plates 354 and discs 356 of the overdrive clutch assembly 304 together against the reaction plate 364 and produces a frictional force between them. Because the input clutch retainer 326 and overdrive clutch plates 354 are rotating, the frictional force causes the overdrive clutch discs 356 and overdrive clutch hub 358 to rotate, in turn, rotating the first planet carrier 508 and second annulus gear 542. When the hydraulic fluid to the overdrive clutch assembly 304 or first hydraulic piston 386 is vented, the deflected spring 404 applies a force to the first hydraulic piston 386, thereby returning the first hydraulic piston 386 to its non-applied position as shown in the figure.

To apply the reverse clutch assembly 306, hydraulic pressure from fluid entering between the first hydraulic piston 386 and input clutch retainer hub 312 move or pushes the first hydraulic piston 386 axially, thereby deflecting the spring 404. The pressure plate member 408 of the first hydraulic piston 386 forces the clutch plate 370 and discs 372 of the reverse clutch assembly 306 together against the reaction plate 380 and produces a frictional force between them. Because the input clutch retainer 326 and reverse clutch plate 370 are rotating, the frictional force causes the reverse clutch discs 372 and reverse clutch hub 374 to rotate, in turn, rotating the first sun gear 506. When the hydraulic fluid to the reverse clutch assembly 306 or first hydraulic piston 386 is vented, the deflected spring 404 applies a force to the first hydraulic piston 386, thereby returning the first hydraulic piston 386 to its non-applied position as shown in the figure.

At the output end of the transmission 100, the two/four shift clutch 308 and low/reverse clutch 310 assemblies are used to hold a particular gear element of the gear assembly 500 against rotation by coupling it to the relatively stationary transmission case 102. To apply the two/four shift clutch assembly 308, hydraulic pressure from fluid entering between the third hydraulic piston housing 452 and the third hydraulic piston 448 moves the third hydraulic piston 448 axially, thereby deflecting the spring 444. The third hydraulic piston 448 forces the clutch plates 434 and discs 436 of the two/four shift clutch assembly 308 together against the reaction plate 445 and produces a frictional force between them. Because the two/four clutch plates 434 do not rotate or are stationary, as they are connected to the transmission case 102, the frictional force holds the two/four clutch discs 436 stationary, in turn, holding the flange 442, reverse hub member 374 and first sun gear 506 stationary. When the hydraulic fluid to the two/four shift clutch assembly 308 or third hydraulic piston 448 is vented, the deflected spring 444 applies a force to the third hydraulic piston 448, thereby returning the third hydraulic piston 448 to its non-applied position as shown in the figure.

To apply the low/reverse clutch assembly 310, hydraulic pressure from fluid entering between the fourth hydraulic piston housing 476 and the fourth hydraulic piston 474 moves the fourth hydraulic piston 474 axially, thereby deflecting the spring 490. The fourth hydraulic piston 474 forces the clutch plates 466 and discs 468 of the low/reverse clutch assembly 310 together against reaction plate 445 and produces a frictional force between them. Because the low/reverse clutch plates 466 are stationary, as they are connected to the transmission case 102, the frictional force holds the low/reverse clutch discs 468 stationary, in turn, holding the second annulus gear 542 and first planet carrier 508 stationary. When the hydraulic fluid to the low/reverse clutch assembly 474 or fourth hydraulic piston 474 is vented, the deflected spring 490 applies a force to the fourth hydraulic piston 474, thereby returning the fourth hydraulic piston 474 to its non-applied position as shown in the figure.

OPERATION OF PLANETARY GEARS

In the neutral N or park P modes of transmission operation, the input shaft 176 (which is attached to the turbine assembly 128) freely rotates with the engine crankshaft 114. Since the input clutch retainer hub 312 is also attached to the input shaft 176, the input clutch retainer hub 312 rotates, in turn, causing the input clutch retainer 326 and clutch plates 342, 354 and 370 to freely rotate with the engine crankshaft 114.

When the transmission 100 is desired to operate in first gear, the underdrive clutch assembly 302 and low/reverse clutch assembly 310 are applied. Hydraulic fluid moves the second hydraulic piston 410 axially away from the torque converter 110 to engage the clutch plates 342 and friction discs 344 of the underdrive clutch assembly 302. This engagement causes the underdrive clutch hub 350 to rotate which, in turn, rotates the gear shaft 352. Because the second sun gear 520 is splined at 522 to the gear shaft 352, rotation of the gear shaft 352 causes the second sun gear 520 to rotate. As the low/reverse clutch assembly 310 is applied by the engagement of the low/reverse clutch plates 466 with the discs 468 the second annulus gear 542 is held stationary. Since the second annulus gear 542 is connected to the first planet carrier 508, the first planet carrier 508 is held stationary. As a result, rotation of the second sun gear 520 causes rotation of the second pinion gears 528 and the second planet carrier 524. Because the output gear 534 is splined at 532 to the second planet carrier 524, rotation of the second planet carrier 524 causes the output gear 534 to rotate. Since the second planet carrier 524 rotates, the first annulus gear 519 also rotates, causing the first pinion gears 510 and first sun gear 506 to freely rotate in first gear. The output gear 534 then transfers the torque from the second planetary carrier 524 to the transfer gear (not shown).

When the transmission 100 is desired to operate in second gear, the underdrive clutch assembly 302 and the two/four shift clutch assembly 308 are applied. Once again, the underdrive clutch hub 350 rotates as described above which, in turn, rotates the gear shaft 352. Rotation of gear shaft 352 causes the second sun gear 520 to rotate. As the two/four shift clutch assembly 308 is applied by engagement of the two/four shift clutch plates 434 with the discs 436, the flange 442, reverse clutch hub 374 and first sun gear 506 are held stationary. Because the transmission 100 has been operating in first gear, the first annulus gear 519 and second planet carrier 524 have been rotating at output speed. Also, the first sun gear 506 has been rotating freely. By holding the first sun gear 506 stationary, the first pinion gears 510 and first planet carrier 508 increase in speed. As a result, the first annulus gear 519, second planet carrier 524 and the output gear 534 rotate at a greater r.p.m. than first gear.

When the transmission 100 is desired to operate in third gear, the underdrive clutch assembly 302 and the overdrive clutch assembly 304 are applied. Once again, engagement of the underdrive clutch assembly 302 causes the second sun gear 520 to rotate as previously described. As the overdrive clutch assembly 304 is applied by engagement of the clutch plates 354 and discs 356 of the overdrive clutch assembly 304, the overdrive clutch hub 358 rotates, in turn, rotating the first planet carrier 508 due to the spline connection at 516. Since the first planet carrier 508 rotates, the first pinion gears 510, first sun gear 506 and second annulus gear 542 also rotate. As a result, the second pinion gears 526 of the second planet carrier 524 rotate, causing the second planet carrier 524 to rotate which, in turn, rotates the output gear 534 at input speed or a higher r.p.m. than second gear.

When the transmission 100 is desired to operate in fourth gear, the overdrive clutch assembly 304 and two/four shift clutch assembly 308 are applied. Application of the overdrive clutch assembly 304 causes the overdrive clutch hub 358 to rotate, as previously described. Rotation of the overdrive clutch hub 358 causes the first planet carrier 508 and second annulus gear 542 to rotate. Application of the two/four shift clutch assembly 308 causes the flange 442, reverse clutch hub 374 and first sun gear 506 to be held stationary as previously described. As a result, rotation of the first planet carrier 508 causes the first pinion gears 510, first annulus gear 519 and second annulus gear 542 to rotate. Rotation of the first and second annulus gears 519 and 542, respectively, causes the second pinion gears 526 and second planet carrier 524 to rotate which, in turn, rotates the output gear 534 at a greater r.p.m. than third gear.

When the transmission 100 is desired to operate in reverse gear, the reverse clutch assembly 306 and low/reverse clutch assembly 310 are applied. The reverse clutch assembly 306 is applied by engagement of the reverse clutch plate 370 and discs 372. This engagement causes the reverse clutch hub 374 to rotate which, in turn, rotates the first sun gear 506. Application of the low/reverse clutch assembly 310 causes the first planet carrier 508 and the second annulus gear 542 to be held stationary as previously described. As a result, the first sun gear 506 rotates the first pinion gears 510 which, in turn, rotate the first annulus gear 519 backwards. Rotation of the first annulus gear 519 causes the second planet carrier 524 and second pinion gears 526 to rotate which, in turn, causes rotation of the output gear 534 in a direction opposite to the other gear positions. Rotation of the second pinion gears 526 also causes the second sun gear 520 to rotate freely.

HYDRAULIC SYSTEM STRUCTURE

The function of the hydraulic system is to cooperate with the electronic controls to make the transmission 100 fully automatic. Referring to FIGS. 3A through 3L, a schematic diagram of the hydraulic system 600 for controlling and operating the fluid flow throughout the transmission 100 is shown. The pump assembly 200, clutch assemblies 302, 304, 306, 308 and 310, torque converter assembly 110 of FIG. 1, and valves to be described herein, are connected by a plurality of internal passageways, generally indicated at 602, in or between the valve body 603, transfer plate (not shown) and transmission case 102.

The fluid source of the transmission 100 is the fluid contained in the transmission pan (not shown) which acts as a reservoir. A filter 605 is attached to the lower half of a transfer plate at the inlet of the transfer plate to prevent dirt and other foreign matter from entering the hydraulic system 600. Another filter (not shown) is disposed in the valve body 60 at the pump pressure inlet to a pressure regulator valve 608 to protect the pressure regulator valve 608 from any loose chips and dirt in the pump hydraulic circuit.

The pump assembly 200 is also connected by the passageways 602 to a manual valve 604 which is coupled to the manually actuated shift lever or manual shaft 591. The manual shaft 591 is connected to the manual lever 578 (FIG. 2), its shift lever position PRNODDL being generally indicated by numeral 606. The pump assembly 200 is further connected by passageways 602 to a pressure regulator valve 608 and to a solenoid or fluid switch valve 610. The passageways 602 also connect the pressure regulator 608 to a cooler or torque converter (T/C) control valve 612. The passageways 602 also connect the T/C control valve 612 to a lock-up (LU) switch valve 614. The passageways 602 further connect the LU switch valve 614 to the torque converter 110, and they also provide a path from the torque converter 110 back to the LU switch valve 614 and to T/C control valve 612. A cooler 616 is connected by passageways 602 to the T/C control valve 612. The manual valve 604 is also connected by passageways 602 to an underdrive element or clutch apply cavity 618, an overdrive clutch apply cavity 620, reverse clutch apply cavity 622 and a two/four shift clutch apply cavity 624. A low/reverse clutch apply cavity 626 is connected by passageways 602 to the solenoid switch valve 610 and, in turn, to the manual valve 604.

The clutch apply cavities 618, 620, 622, 624 and 626 are also identified in FIGS. 1C and 1D. The valves 604 and 610 are also connected by passageways 602 to a vent reservoir 628 in the manifold assembly 700 which is at a higher elevation than the sump or fluid reservoir in the transmission pan. The other valves vent to the sump as indicated by the letter "V".

The hydraulic system 600 also includes an underdrive element or clutch solenoid-actuated valve 630, overdrive clutch solenoid-actuated valve 632, two/four shift clutch solenoid-actuated valve 634 and low/reverse clutch solenoid-actuated valve 636 which will be described. The solenoid-actuated valves 630, 632, 634 and 636 control the fluid flow to their respective clutch apply cavities 618, 620, 624 and 626.

The manual valve 604 controls the fluid flow to the reverse clutch apply cavity 622. The low/reverse clutch solenoid-actuated valve 636 includes a second or dual function of controlling fluid flow to the LU switch valve 614 during lock-up of the torque converter 110 (FIGS. 3G, 3I, 3J, 3L). The two/four clutch solenoid-actuated valve 634 also has a dual function of controlling fluid flow to the low/reverse clutch apply cavity 626 when the shift lever position 606 is reverse (FIG. 3C). These solenoid-actuated valves 630, 632, 634 and 636 operate in response to command or control signals from the electronic controls.

In one embodiment according to the present invention, both the underdrive clutch solenoid-actuated valve 630 and two/four shift clutch solenoid-actuated valve 634 are designed to be normally applied. This means that in the absence of electrical power, the solenoid-actuated valves 630 and 634 will allow pressure or fluid flow in the passageways 602 to be transmitted to the underdrive clutch apply cavity 618 and two/four shift clutch apply cavity 624, respectively. Hence, the underdrive clutch assembly 302 and two/four shift clutch assembly 308 will be applied, resulting in the transmission 100 operating in second gear. Likewise, the overdrive clutch solenoid-actuated valve 632 and low/reverse clutch solenoid-actuated valve 636 are designed to be normally vented. This means that in the absence of electrical power, the solenoid-actuated valves 632 and 636 will vent fluid in passageways 602 and thus prevent fluid flow to the overdrive clutch apply cavity 620 and low/reverse clutch apply cavity 626, respectively. Hence, the overdrive clutch assembly 304 and low/reverse clutch assembly 310 will not be applied so that the transmission 100 may operate in second gear.

The hydraulic system 600 also includes accumulators 638, 640, 642 and 644 which are connected to passageways 602 before the underdrive 618, overdrive 620, two/four shift 624 and low/reverse 626 clutch apply cavities, respectively. The accumulators 638, 640, 642 and 644 comprise a first spring 645a, a second spring 645b and a piston 645c operating in a bore 645d in the valve body 603. The purpose of these accumulators 638, 640, 642 and 644 is to absorb the fluid apply pressure to help cushion the application of the underdrive 302, overdrive 304, two/four shift 308 and low/reverse 310 clutch assemblies, respectively.

As illustrated in FIGS. 3A-3L, pressure switches 646, 648 and 650 are connected to the passageways 602 which lead to the overdrive clutch apply cavity 620, the two/four shift clutch apply cavity 622 and the low/reverse clutch apply cavity 626, respectively. The pressure switches 646, 648 and 650 provide a digital electrical signal of zero (0) value when there is either an absence of fluid pressure or fluid pressure below a predetermined pressure, and a value of one (1) when there is fluid pressure present at or above a predetermined pressure in the passageway 602 leading to the respective clutch apply cavities 620, 624 and 626. However, it should be appreciated that other suitable pressure sensors may be employed in these or other locations in the appropriate application.

The hydraulic system 600 also includes first 652, second 654, third 656, fourth 658 and fifth 660 ball check valves in the passageways 602 leading to the low/reverse 626, underdrive 618, low/reverse 626, reverse 622 and overdrive 620 clutch apply cavities, respectively. The ball check valves 652, 654, 656, 658 and 660 comprise a rubber ball operating against a seat, typically formed in the valve body 603, and are used for flow control to open and close particular passageways 602. The ball is seated by pressure acting against the ball and unseated by pressure being applied on the opposite or seat side of the ball.

As illustrated in FIGS. 3A through 3L, the LU switch valve 614, T/C control valve 612 and pressure regulator 608 include springs 662, 664 and 666, respectively, at one end to preload these valves. A thermal valve 668 is also provided to regulate the fluid flow through check valve 654 at higher fluid temperatures. The thermal valve 668 closes or opens a particular passageway 602 based on the fluid temperature.

OPERATION OF THE HYDRAULIC SYSTEM

As illustrated in FIGS. 3A-L, the hydraulic system 600 is shown. The dense shading or hatching in the passageways 602 shows fluid at pump pressure. The sparse shading or hatching illustrates a low fluid pressure. The intermediate shading or hatching illustrates a fluid pressure between that of pump pressure and a low pressure. The absence of shading or hatching shows the passageways 602 as vented.

When the engine is initially started, the pressure regulator 608 is actuated or moved by fluid pressure to allow fluid from the pump assembly 200 to flow through the pressure regulator 608 between the first 670a and second 670b lands to the T/C control valve 612, as illustrated in FIG. 5A. The T/C control valve 612 is similarly actuated by fluid pressure to allow fluid from the pressure regulator 608 to flow between the first 672a and second 672b lands of the T/C control valve 612 to the LU switch valve 614. Fluid then flows between the first 674a and second 674b lands of the LU switch valve 614 to the torque converter 110. This fluid pressure moves the lock-up piston 188 off or in disengagement with the friction disc 199 of the lock-up clutch assembly 186 so that lock-up is not applied. Fluid also flows from the torque converter 110 back to the T/C control valve 612. Fluid flows between the second 674b and third 674c lands thereof and through the cooler 616 where it is cooled and used for lubrication.

As illustrated in FIG. 3A, when the shift lever position 606 is park P or neutral N with the output speed N_(o) from the transmission's output speed sensor 546 less than 600 r.p.m., fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands to the low/reverse clutch solenoid-actuated valve 636 which is energized by the transmission controller 3010 and moves to allow fluid to flow through it to the solenoid switch valve 610. The solenoid switch valve 610 is hydraulic or fluid pressure operated for reciprocal movement between a first position shown in FIG. 3E and a second position shown in FIG. 3F.

Fluid flows through the solenoid switch valve 610 between the second 678b and third 678c lands thereof to the first ball check valve 652. The first ball check valve 652 is moved by fluid pressure to close the flow path to the vent through the manual valve 604 and opens the flow path to the low/reverse clutch apply cavity 626. Fluid flows through the first ball check valve 652 to the low/reverse clutch apply cavity 626 behind the fourth hydraulic piston 474 to apply the low/reverse clutch assembly 310 in a manner controlled by the command signal from the transmission controller 3010 sent to the low/reverse clutch solenoid-actuated valve 636.

As illustrated in FIG. 3A, fluid flows from the manual valve 604 and solenoid switch valve 610 to both sides of the third ball check valve 656. In this case, the third ball check valve 656 is redundant.

The manual valve 604 also allows fluid in the clutch apply cavity 624 of the two/four shift clutch assembly 308 to vent to the vent reservoir 628, resulting in this clutch not being engaged or applied. Similarly, fluid in the clutch apply cavity 618 of the underdrive clutch assembly 30 is vented either through the manual valve 604 to the sump or through the underdrive clutch solenoid-actuated valve 630. Some fluid from the torque converter 110 also flows through the bleeder ball check valves 244 and 246 to the overdrive 620 and reverse 622 clutch apply cavities as previously described. However, the overdrive 304 and reverse 306 clutch assemblies are essentially vented and not applied.

Fluid from the pump assembly 200 also flows to the solenoid switch valve 610 at one end of the first land 678a to pressure balance solenoid switch valve 610. In other words, fluid flow pressurizes one end of the solenoid switch valve 610 to allow the valve to maintain its current position and prevent the valve from moving to one end or the other past its desired or proper position. Fluid also flows from the pump assembly 200 to the LU switch valve 614 between the third 674c and fourth 674d lands and is dead-ended. This is because the LU switch valve 614 is a single diameter valve, therefore no resultant force exists to overcome the spring force of spring 666. Additionally, fluid from the pump assembly 200 flows to one end of a plug 680 of the pressure regulator 608 to pressure balance the pressure regulator 608. Fluid from the pump assembly 200 further flows to the two/four shift clutch solenoid-actuated valve 634. However, this valve is energized by the transmission controller 3010 and moves to block or close fluid flow to the two/four shift clutch apply cavity 624.

As illustrated in FIG. 3B, when the shift lever position 606 is neutral N with the output speed N_(o) from the transmission's output speed sensor 546 greater than 600 r.p.m., fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands to the third ball check valve 656. This fluid pressure moves the third ball check valve 656 to close the flow path to the low/reverse clutch apply cavity 626. Hence, the low/reverse clutch assembly 310 is not applied, but vented through the first ball check valve 652 to either the low/reverse clutch solenoid-actuated valve 636 or the manual valve 604. This prevents the transmission 100 from being shifted into a drive mode OD, D or L above an undesired output speed N_(o), i.e. 600 r.p.m. Fluid from the manual valve 604 also flows to the low/reverse clutch solenoid-actuated valve 636 which is off or de-energized (i.e. normally vented) and closes the flow path to the solenoid switch valve 610.

The manual valve 604 further allows fluid in the clutch apply cavity 624 of the two/four shift clutch assembly 308 to vent to the vent reservoir 628, resulting in this clutch not being engaged or applied. Fluid in the clutch apply cavity 618 of the underdrive clutch assembly 302 vents through the underdrive clutch solenoid-actuated valve 630 to vent the reservoir 628, resulting in this clutch not being engaged or applied. The overdrive 304 and reverse 306 clutch assemblies receive some fluid but are vented or not applied as previously described. Fluid from the pump assembly 200 also flows to one end of the first land 678a of the solenoid switch valve 610 to hold it in a position for fluid communication by the passageways 602 between the low/reverse clutch solenoid-actuated valve 636 and the clutch apply cavity 626 of the low/reverse clutch assembly 310. Fluid also flows from the pump assembly 200 to the LU switch valve 614 and pressure regulator 608 as previously described. Additionally, fluid from the pump assembly 200 further flows to the two/four shift clutch solenoid-actuated valve 634. However, this valve is energized to block fluid flow as previously described.

As illustrated in FIG. 3C, when the shift lever position 606 is reverse R, the manual valve 604 attached to the manual lever 578 is moved or shifted. Fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands and through an orifice 682 to the reverse clutch apply cavity 622 between the second hydraulic piston 410 and input clutch retainer hub 312 to apply the reverse clutch assembly 306. Fluid flows to both sides of the fourth ball check valve 658 making it redundant. However, the fourth ball check valve 658 allows fluid flow from the reverse clutch apply cavity 622 to bypass the orifice 682 when venting the reverse clutch apply cavity 622 through the manual valve 604.

The manual valve 604 also allows fluid in the clutch apply cavity 624 of the two/four shift clutch assembly 308 to vent to the vent reservoir 628, resulting in this clutch not being engaged or applied. Fluid in the clutch apply cavity 618 of the underdrive clutch assembly 302 vents through the underdrive clutch solenoid-actuated valve 630. The overdrive clutch assembly 304 receives some fluid but is vented or not applied as previously described. Fluid to the reverse clutch apply cavity 622 causes the reverse bleeder ball check valve 246 to close as previously described.

Fluid from the pump assembly 200 flows through the two/four shift clutch solenoid-actuated valve 634, which is not energized or applied normally, to the manual valve 604. Fluid flows through the manual valve 604 between the third 676c and fourth 676d lands of the manual valve 604 to the first ball check valve 652. This fluid pressure moves the first ball check valve 652 to close the flow path to the solenoid switch valve 610 and opens the flow path to the low/reverse clutch apply cavity 626 behind the fourth hydraulic piston 474 to apply the low/reverse clutch assembly 310. Fluid from the pump assembly 200 further flows to one end of the first land 678a of the solenoid switch valve 610 and the LU switch valve 614 as previously described. Additionally, fluid flows to both ends of the plug 680 of the pressure regulator 608. Since the pressure area of the plug 688 is smaller than plug 680, the valve 680 is shifted, creating a new fluid line pressure.

As illustrated in FIG. 3D, when the shift lever position 606 is reverse R and the output speed N_(o) is greater than 600 r.p.m., fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands and through the orifice 682 to the reverse clutch apply cavity 622 between the second hydraulic piston 410 and the input clutch retainer hub 312 to apply the reverse clutch assembly 306. The two/four shift clutch solenoid-actuated valve 634 is energized by the transmission controller 3010 and moves to prevent fluid flow to the manual valve 604, resulting in the low/reverse clutch 310 not being applied. This prevents the transmission 100 from being shifted into the reverse mode above an undesired output speed N_(o), i.e. 600 r.p.m.

Fluid in the clutch apply cavities 624, 618 and 620 of the two/four shift clutch 308, underdrive clutch 302 and overdrive clutch 304 assemblies, respectively, are vented as previously described, resulting in these clutches not being engaged or applied. The overdrive clutch assembly 304 receives some fluid but is vented or not applied as previously described. Otherwise, fluid flow is similar to the reverse hydraulic schematic of FIG. 3C as previously described.

As illustrated in FIG. 3E, when the shift lever position 606 is the drive D position, overdrive OD or low L, the transmission 100 is operated initially in first gear. As a result, the manual valve 604 is moved or shifted. Fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands to the underdrive clutch solenoid-actuated valve 630. The underdrive clutch solenoid-actuated valve 630 which is normally applied, allows fluid to flow through it and the flow path to the underdrive clutch apply cavity 618 behind the second hydraulic piston 410 to apply the underdrive clutch assembly 302.

Fluid from the manual valve 604 also flows to the second ball check valve 654 which is pressurized from both sides and becomes redundant. Fluid from the manual valve 604 moves the fifth ball check valve 660 to close the flow path to the overdrive clutch apply cavity 620. Fluid from the manual valve 604 further flows to the overdrive clutch solenoid-actuated valve 632 which is normally vented and is prevented from flowing through the flow path to the overdrive clutch apply cavity 620.

Fluid further flows to both sides of the third ball check valve 656, making it redundant. Fluid from the manual valve 604 also flows to the low/reverse clutch solenoid-actuated valve 636. The low/reverse clutch solenoid-actuated valve 636 is energized by the transmission controller 3010 and moves to open the flow path to the solenoid switch valve 610. Fluid flows through the solenoid switch valve 610 between the second 678b and third 678c lands to the low/reverse clutch apply cavity 626 behind the fourth hydraulic piston 474 to apply the low/reverse clutch assembly 310.

Fluid in the clutch apply cavity 624 of the two/four shift clutch assembly 308, is vented as previously described, resulting in this clutch not being engaged or applied. Fluid in the clutch apply cavity 620 of the overdrive clutch assembly 304 is vented through the overdrive clutch solenoid-actuated valve 632. Fluid in the clutch apply cavity 622 of the reverse clutch assembly 306 is vented through the manual valve 604. Hence, the overdrive 304 and reverse 306 clutch assemblies are essentially vented and not applied as previously described.

Fluid from the pump assembly 200 also flows to one end of the first land 678a of the solenoid switch valve 610, the LU switch valve 614, and one end of the plug 680 of the pressure regulator 608 as previously described. Fluid from the pump assembly 200 also flows to the two/four shift clutch solenoid-actuated valve 634. However, this valve is energized and moved to engage its seat to block fluid flow as previously described.

Referring to FIG. 3F, the operation of the hydraulic system is illustrated when the transmission 100 is shifted into second gear. It should be noted that none of the solenoid-actuated valves 630, 632, 634 and 636 are energized, so that they will each assume their normally open (applied) or closed (vented) positions as described earlier.

As illustrated in FIG. 3F, when the shift lever position 606 is in the overdrive OD, drive D or low L position, and the transmission 100 is to be operated in second gear, the manual valve 604 remains in the same position as first gear. Fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands to the underdrive clutch solenoid-actuated valve 630 which is normally applied and allows fluid flow to the underdrive clutch apply cavity 618 as previously described. Fluid also flows from the manual valve 604 to the overdrive clutch solenoid-actuated valve 632 which is normally vented and prevents fluid flow to the overdrive clutch apply cavity 620. Fluid from the manual valve 604 also flows to the second and fifth ball check valves 654 and 660 as previously described.

Fluid from the pump assembly 200 also flows to the two/four shift clutch solenoid-actuated valve 634 which is normally applied and allows fluid flow to the manual valve 604. Fluid flows between the third 676c and fourth 676d lands of the manual valve 604 to the two/four shift clutch apply cavity 624 behind the third hydraulic piston 448 to apply the two/four shift clutch assembly 308. Fluid also flows between one end of fifth land 678e of the solenoid switch valve 610 and a plug 684. Because the pressure area of fifth land 678e is larger than the pressure area of first land 678a, when these lands 678a and 678e are exposed to the same pressure, the solenoid switch valve 610 is moved to the left as shown in the figure. Hence, the solenoid switch valve 610 is moved by fluid pressure acting on it to allow fluid to flow through the solenoid switch valve 610 between the fourth 678d and fifth 678e lands and to one end of a plug 686 thereof to pressure balance the solenoid switch valve 610.

Fluid in the clutch apply cavity 626 of the low/reverse clutch assembly 308 is vented as previously described, resulting in this clutch not being engaged or applied. The overdrive 304 and reverse 306 clutch assemblies are also vented as previously described. Fluid from the pump assembly 200 further flows through the LU switch valve 614 to one end of plug 680 of the pressure regulator 608 as previously described.

As illustrated in FIG. 3G, when the partial lock-up feature is used in second gear, the LU switch valve 614 is moved or shifted by fluid pressure, from the low/reverse clutch solenoid-actuated valve 636 and the solenoid switch valve 610, to close fluid flow from the T/C control valve 612 to the lock-up clutch assembly 186 of the torque converter 110 because it is dead-ended at second land 674b of the LU switch valve 614. This results in fluid flow from the lock-up clutch assembly 186 being vented at the LU switch valve 614. Fluid flow from the pump assembly 200 to the torque converter 110 causes the lock-up piston 188 to engage the friction disc 199 of the torque converter 110. Lock-up of the torque converter 110 occurs as previously described. The low/reverse clutch solenoid-actuated valve 636 is cycled or modulated (MOD) by command signals from the transmission controller 3010 to allow fluid to flow between the third 678c and fourth 678d lands of the solenoid switch valve 610 to one end of the fourth land 674d of the LU switch valve 614 to actuate or cycle it by fluid pressure, resulting in partial lock-up of the torque converter 110. Fluid also flows to one end of the fourth land 672d of the T/C control valve 612. This is because the fluid to one end of the fourth land 672d moves the T/C control valve 614 to one end of its valve bore and the fluid fluid configuration maintains the valve's position during the off period of the duty cycle, causing quick torque build-up by the lock-up clutch 186 and slow torque loss rate by lock-up clutch 186 (i.e. goes to unlock more slowly).

As illustrated in FIG. 3H, when the operating mode of the transmission 100 is to be third gear, the manual valve 604 remains in the same position as first gear. Fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands to the underdrive clutch solenoid-actuated valve 630 which is normally applied and allows fluid flow to the underdrive clutch apply cavity 618 as previously described. Fluid from the manual valve 604 also flows to the overdrive clutch solenoid-actuated valve 632 which is energized by the transmission controller 3010 and moves to open the flow path to the overdrive clutch apply cavity 620 behind the first hydraulic piston 386 to apply the overdrive clutch assembly 304.

Fluid from the manual valve 604 further flows to the third ball check valve 656 which is moved to close the flow path to the low/reverse clutch apply cavity 626. Fluid also flows to the low/reverse clutch solenoid-actuated valve 636 which is normally vented and is prevented from flowing through the flow path to the solenoid switch valve 610. Fluid from the underdrive clutch solenoid-actuated valve 630 also flows to the solenoid switch valve 610 between the fourth 678d and fifth 678e lands and to both sides of plug 686 of the solenoid switch valve 610 as previously described. Fluid from the overdrive clutch solenoid-actuated valve 632 flows between land 670c and plug 688 and sleeve 690 of the pressure regulator valve 608. Since fluid pressurized plug 680 has the same contact or pressure area as plug and sleeve 688, 690, these plugs are redundant. Hence, pressure area of third land 670c is the only active area, moving the pressure regulator 608 and causing a new line pressure.

Fluid in the clutch apply cavities 626 and 624 of the low/reverse clutch 310 and two/four shift clutch assemblies 308, respectively, is vented as previously described, resulting in these clutches not being engaged or applied. The reverse clutch assembly 306 receives some fluid and is essentially vented as previously described. Fluid from the pump assembly 200 also flows to the LU switch valve 614 as previously described. Fluid from the pump assembly 200 further flows to the two/four shift clutch solenoid-actuated valve 634. However, this valve is energized by the transmission controller 3010 and moves to block fluid flow as previously described.

As illustrated in FIG. 3I, when the partial lock-up feature is used in third gear, the LU switch valve 614 is moved by fluid pressure to prevent fluid flow from the T/C control valve 612 from reaching the lock-up clutch assembly 186 as previously described. Thus, fluid flow is vented from the lock-up clutch assembly 186 of the torque converter 110 at the LU switch valve 614. Fluid from the pump assembly 200 flows through the LU switch valve 614 between the third 674c and fourth 674d lands to the torque converter 110, causing the lock-up piston 188 to engage the friction disc 199 resulting in lock-up of the torque converter 110. Further, fluid from the torque converter 110 flows through the T/C control valve 612 past the cooler 616 and is used for lubrication. The low/reverse clutch solenoid-actuated valve 636 is cycled by command signals from the transmission controller 3010 to allow fluid flow from the manual valve 604 through the solenoid switch valve 610 to one end of fourth land 674d of the LU switch valve 614 and fourth land 672d of the T/C control valve 612 to actuate or cycle these valves for partial lock-up of the torque converter 110 as previously described.

As illustrated in FIG. 3J, when the full lock-up feature is used in third gear, the lock-up switch valve 614 is moved by fluid pressure to prevent fluid from the T/C control valve 612 from reaching the lock-up assembly 186 as previously described. The low/reverse clutch solenoid-actuated valve 636 is energized by the transmission controller 3010 and moves to allow full fluid flow from the manual valve 604 through the solenoid switch valve 610 to one end of fourth land 674d of the LU switch valve 614 and fourth land 672d of the T/C control valve 612 as previously described. In other words, the low/reverse clutch solenoid-actuated valve 636 is not cycled, but energized fully for a predetermined time period, preventing the LU switch valve 614 from being cycled and resulting in full lock-up of the torque converter 110.

As illustrated in FIG. 3K, when the operating mode of the transmission 100 is to be fourth gear in the overdrive OD position, fluid flows from the pump assembly 200 to the manual valve 604. Fluid flows through the manual valve 604 between the first 676a and second 676b lands to the second ball check valve 654. The second ball check valve 654 is moved by fluid pressure to close one flow path to the underdrive clutch apply cavity 618. Fluid flows from the manual valve 604 to the underdrive clutch solenoid-actuated valve 630 which is energized by the transmission controller 3010 and moves to close the other flow path to the underdrive clutch apply cavity 618. Fluid also flows from the manual valve 604 to the overdrive clutch solenoid-actuated valve 632 which is energized by the transmission controller 3010 and moves to open the flow path to the overdrive clutch apply cavity 620. Fluid from the manual valve 604 also flows to the low/reverse clutch solenoid-actuated valve 636 which is normally vented, preventing fluid flow to the solenoid switch valve 610. Fluid from the manual valve 604 further flows to the third ball check valve 656 which is moved to close the flow path to the low/reverse clutch apply cavity 626. Fluid from the pump assembly 200 further flows to the two/four shift clutch solenoid-actuated valve 634 which is normally applied and allows fluid flow through it to the manual valve 604. Fluid flows between the third 676c and fourth 676d lands of the manual valve 604 to the two/four shift clutch apply cavity 624.

Fluid in the clutch apply cavities 626 and 618 of the low/reverse clutch 310 and underdrive clutch 302 assemblies, respectively, is vented as previously described, resulting in these clutches not being engaged or applied. The reverse clutch assembly 306 receives some fluid but is essentially vented as previously described. Fluid from the pump assembly 200 also flows to the lock-up switch valve 614 and to the pressure regulator 608 as previously described.

As illustrated in FIG. 3L, when the full lock-up feature is used in fourth gear, the LU switch valve 614 is moved by fluid pressure to prevent fluid flow from the T/C control valve 612 from reaching the lock-up clutch assembly 186. Thus, fluid flow is vented from the lock-up clutch assembly 186 of the torque converter 110 to the sump as previously described. The low/reverse clutch solenoid-actuated valve 648 is energized by the transmission controller 3010 for a predetermined time period and moves to allow full fluid flow from the manual valve 604 through the solenoid switch valve 610 to one end of the fourth land 674d of LU switch valve 614 and the fourth land 672d of the T/C control control valve 612 as previously described, resulting in full lock-up of the torque converter 110.

LIMP-HOME MODE PROTECTION

Since a limp-home mode is typically needed in the presence of a failure, it must be designed to have virtually absolute reliability. Accordingly, the transmission controller 3010 is designed with a master power relay which will only remain energized with full and proper controller operation, thus assuring the ability to achieve a power-Off state. The solenoid state in limp-home is "Off" or de-energized. Therefore, the Off or "normal" state of the solenoid-actuated valves 630, 632, 634, 636 provide the needed clutch application. The solenoid-actuated valves 630, 632, 634, 636 are ball-type valves which function without any dirt-sensitive close clearances and which will be effective even with dirt on the valve seat. The manually actuated valve 604 is the only component which must function to achieve second gear in OD, D or L, neutral in N, reverse in R and park in P.

Referring to FIG. 3F which illustrates the hydraulic schematic for second gear operation, fluid flows through the manual valve 604 between the first 676a and second 676b lands and through the underdrive clutch solenoid-actuated valve 630 which is normally applied, to the underdrive clutch apply cavity 618 as previously described. Fluid also flows from the manual valve 604 to the overdrive clutch solenoid- actuated valve 632 which is normally vented and is prevented from flowing to the overdrive clutch apply cavity 618. Fluid from the manual valve 604 also flows to the third ball check valve 656 which closes the flow path to the low/reverse clutch apply cavity 626. The manual valve 604 further allows fluid in the overdrive clutch 304, reverse clutch 306 and the low/reverse clutch 308 assemblies to vent as previously described, resulting in these clutches not being engaged or applied. Fluid from the pump assembly 200 also flows through the two/four clutch solenoid-actuated valve 634 which is normally applied to the manual valve 604. Fluid then flows between the third 676c and fourth 676d lands of the manual valve 604 to the two/four shift clutch apply cavity 624 as previously described. Hence, second gear is achieved.

It is also important to note that the limp-home mode protection feature of the present invention is also designed to allow reverse gear to be used. The transmission 100 will operate in accordance with the hydraulic schematic of FIG. 3C in order to permit use of the transmission's reverse gear. However, all of the solenoid-actuated valves will be in their "normal" state.

It is further important to note that the limp-home mode protection feature of the prevent invention is also designed to allow park and neutral operating modes to be used. The transmission 100 will operate in accordance with the hydraulic schematic of FIG. 3A except that all of the solenoid-actuated valves will be in their "normal" state.

TRANSMISSION CONTROL METHOD

Referring to FIG. 4, the logic or methodology of the transmission controller 3010 is shown at 800. When the key of the vehicle is turned on, power-up of the transmission controller 3010 occurs in bubble 802. Next, the transmission controller 3010 performs or enters a seven millisecond (7 ms.) main program or control loop. At the beginning of the main control loop, the methodology advances to block 804 called shift select to "orchestrate" various methods used to determine the operating mode or gear, i.e. first gear, the transmission 100 is presently in and which gear the transmission 100 should be in next, and comparing the two to each other to determine if a shift is required. The methodology advances to bubble 806 to calculate the speed and acceleration of the turbine 128, output gear 534 and engine crankshaft 114. The transmission controller 3010 receives input data from the turbine speed sensor 320 (turbine speed N_(t), output speed sensor 546 (output speed N_(o)) and engine speed sensor (not shown) (engine speed N_(o)) in circle 808. In bubble 806, the engine speed N_(o), turbine speed N_(t) and output speed N_(o) are calculated from the input data. The methodology advances to bubble 810 called the shift schedule to be described under section heading "SHIFT SCHEDULE METHOD". The shift schedule bubble 810 reads or determines the shift lever position 606, PRNODDL, of the manual lever 578 by contact switch sensors (NS₁, NS₂) (See FIG. 2) in circle 812. The shift schedule bubble 810 also determines the throttle angle THRT ANGLE of the engine, to be described under section heading "THROTTLE ANGLE COMPUTATION AND FAILURE DETECTION", by an input of a potentiometer (not shown) connected to the throttle (not shown) in circle 814. The shift schedule bubble 810 further determines the engine temperature, to be described under section heading "PRESSURE SWITCH TEST AND TRANSMISSION TEMPERATURE DETERMINATION METHOD" in circle 816. The shift schedule bubble 810 uses the data items such as output speed N_(o) in circle 815 (generated by bubble 806), PRNODDL (generated by circle 812) and throttle angle (generated by circle 814) to determine the appropriate gear the transmission 100 should be placed.

The methodology advances to bubble 818 which outputs the appropriate command signals to the solenoid-actuated valves 630, 632, 634 and 636 and properly energizes or de-energizes them based on which gear the transmission 100 is in, as determined by circle 812. The methodology advances to bubble 820 to execute diagnostic or monitoring routines. In diagnostic bubble 820, the transmission controller 3010 determines if the proper pressure switches 646, 648 and 650, previously described, are pressurized by either looking for signals from a specific pressure switch combination for the present in-gear condition of the transmission 100 or from a specific pressure switch to a non-controlling clutch during a pressure switch test to be described. The transmission controller 3010 also determines if the wires in the control system are not shorted or open by looking for a flyback voltage or EMF spike during a solenoid continuity test to be described under section "SOLENOID CONTINUITY TEST METHOD". The methodology then advances to diamond 822 and determines whether a failure has occurred. If a failure has occurred, the methodology advances to block 824 in which the transmission controller 3010 de-energizes the solenoid-actuated valves 630, 632, 634 and 636 which assume their normal positions to allow the transmission 100 to operate in second gear in the drive mode, i.e. limp-home mode previously described. If a failure has not occurred, the methodology advances to the shift select block 804. Based on the calculated speeds and shift schedule output (SSOUTP), the methodology determines if a shift is required. This process is done every 7 ms.

Since the shift select block 804 compares the gear the transmission 100 is presently in, to the SSOUTP, the methodology advances to diamond 826 and determines if a shift or gear change is required. If a shift is required, the methodology advances to block 828 called the shift logic to be described herein. Otherwise, if a shift is not required, the methodology advances to diamond 830 and looks at the lock-up schedules, i.e. a plot of THRT ANGLE verses N_(t), etc., to determine if lock-up of the torque converter 110 is required. If lock-up is not required, the methodology returns to the beginning of the shift select block 804 again for another 7 ms. loop. Otherwise, if lock-up is required, the methodology advances to diamond 832 and determines if the torque converter 110 is presently locked-up by looking for a flag that has previously been set during full lock-up of the torque converter 110. If the torque converter 110 is presently locked-up, the methodology returns to the shift select block 804. Otherwise, the methodology advances to block 834 called partial lock-up logic or methodology, to be described under section heading "TORQUE CONVERTER LOCK-UP METHOD", for the torque converter 110.

If a shift or gear change is needed or required, the shift logic block 828 uses one of twelve unique shift programs or routines. The shift routines are 1-2, 2-3, 2-4, 3-4 (upshifts); 4-3, 4-2, 3-2, 3-1, 2-1, (downshifts); and N-1, R-N, N-R (garage shifts) to be described herein. The shift logic block 828 has to identify the proper shift logic routine, and then execute it. The shift logic block 828 controls the solenoid-actuated valves 630, 632, 634 and 636 to shift the transmission 100 from its present gear to the next gear in a smooth manner.

After the shift logic block 828, the methodology advances to diamond 836 and determines if lock-up of the torque converter 110 is required as previously described. If lock-up is required, the methodology advances to diamond 838 and determines whether the torque converter 110 is already locked-up as previously described. If the torque converter 110 is not already locked-up, the transmission controller 3010 executes the partial lock-up block 834, to be described herein.

The partial lock-up block 834 is used to reduce slip of the torque converter 110. Slip equals N_(o) minus N_(t). The partial lock-up block 834 instructs or causes the transmission 100 to fully lock, partially lock or fully unlock the torque converter 110. If unlock is desired, the transmission controller 3010 will hold the solenoid-actuated valve 636 in the de-energized or normally vented mode to move the LU switch valve 614 and allow fluid pressure to disengage the lock-up clutch 186. If partial lock is desired, the transmission controller 3010 will reduce slip to a low or predetermined desired value, but not completely eliminate it. The transmission controller 3010 calculates the slip by N_(o) minus N_(t) based on the input from the sensors previously described. The transmission controller 3010 compares this to a predetermined desired value of slip, e.g. 60 r.p.m., and thus, determines if the torque converter 110 is slipping too much or too little. If too much slip occurs, the transmission controller 3010 will increase the duty cycle ("ON" time) of the low/reverse clutch solenoid- actuated valve 636 and the LU switch valve 614, which will increase the pressure differential across the lock-up clutch assembly 186 and thus, decrease the slip. This technique is called "pulse-width modulation".

If full lock-up is desired, the transmission controller 3010 will gradually increase the fluid pressure to the lock-up clutch 186, adding more "ON" cycle time to the solenoid-actuated valve 636 thereby increasing the "ON" cycle time at the LU switch valve 614 until maximum, resulting in zero slip.

Returning to diamond 836, if the transmission controller 3010 determines that lock-up of the torque converter 110 is not required, the methodology advances to bubble 840 to execute diagnostic or monitoring routines as previously described. Similarly, if the transmission controller 3010 determines that the torque converter 110 is already locked-up in diamond 838, the methodology advances to bubble 840 to execute diagnostic or monitoring routines as previously described. Further, once the partial lock-up block 834 is completed, the methodology advances to bubble 840 to execute diagnostic or monitoring routines as previously described.

From diagnostic bubble 840, the methodology advances to diamond 842 and determines whether a failure has occurred as previously described. If a failure has occurred, the methodology advances to block 844 and causes the transmission 100 to default to or operate in second gear. Otherwise, if no failure occurs in diamond 842, the methodology advances to diamond 846 and determines if the time period for the diagnostic loop has expired by any suitable method such as looking at a counter. If the time has not expired, the methodology advances to bubble 840 to execute the diagnostic routines again until the time period has expired. If the time period has expired, the methodology advances to bubble 848 to calculate speeds N_(e), N_(t) and N_(o) as previously described. The methodology then advances to bubble 850 to perform another shift schedule as previously described using PRNODDL circle 852, output speed N_(o) circle 855, THRT ANGLE circle 854, and engine temperature circle 856.

To perform the shift in a smooth manner, the transmission controller 3010 slips the clutches of the multi-clutch assembly 300. The transmission controller 3010 has to control the pressure on applying clutches and releasing clutches in an orchestrated manner. To do this, the methodology advances from the shift schedule bubble 850 to bubble 858 and determines the appropriate rate of acceleration, called the "desired acceleration" (alphaa_(desired) or a*) to control the turbine 128. The desired acceleration may be predetermined by an equation, point/slope interpolation or any other suitable method. The methodology advances to bubble 860 and calculates the present acceleration (alpha_(t) or a_(t)) of the turbine 128 based on turbine speed N_(t) which tells the transmission controller 3010 how quickly the shift is happening. The transmission controller 3010 indirectly compares the value of desired acceleration with the calculated acceleration. This may be accomplished by placing the above values into an equation to decide the duty cycle for proportional control to be described. The methodology advances to bubble 862 to output the appropriate command signals to either actuate and/or deactuate (turn logically either "ON" or "OFF") the solenoid-actuated valves 630, 632, 634 and 636 for the engaging (apply) or disengaging (release) of the clutches.

For upshifts, if the turbine 128 is decelerating too fast, the transmission controller 3010 reduces the pressure on the applying clutch by either actuating and/or deactuating the solenoid-actuated valves 630, 632, 634 and 636 in bubble 862. For downshifts, if the turbine 128 is accelerating too rapidly, the transmission controller 3010 increases the pressure on the applying clutch by either actuating and/or deactuating the solenoid-actuated valves 630, 632, 634 and 636 in bubble 862. If the turbine assembly 128 is accelerating at the desired acceleration level, the solenoid-actuated valves 630, 632, 634 and 636 are either actuated and/or deactuated to obtain the shift or gear change. At the end of 7 ms. loop, the methodology advances to diamond 864. The transmission controller 3010 tallies the ratios of N_(t) to N_(o) again to determine if the shift or gear change is complete. If N_(o) and N_(t) are at proper values, i.e. ratio ×N_(o) =N_(o) for a predetermined time period which is different for each shift, the transmission controller 3010 determines that the shift or gear change is complete. The methodology returns to the beginning of the control loop to the shift select block 804. If the shift or gear change is not complete, the methodology returns to the shift logic block 828 to repeat the method as previously described.

SHIFT SCHEDULE METHOD

The shift schedule method determines the appropriate gear in which the transmission 100 should be placed. The shift schedule method first determines the present gear of the transmission 100 by the shift lever position 606 of the manual lever 578 in circle 812 of FIG. 4. Based on the shift lever position 606, the shift schedule method determines the appropriate gear in which the transmission 100 should be placed.

Referring to FIG. 5A, the bubble 810 of FIG. 4 for the shift schedule method is shown. The methodology enters from the shift select block 804 through bubble 900 and advances to diamond 902. At diamond 902, the methodology determines whether the shift lever position (SLP) 606 of the manual lever 578 is park P or neutral N by reading a coded signal from the sensors NS₁ and NS₂ (FIG. 2) to be described. If SLP 606 is park or neutral, the methodology advances to block 904 and sets the new output (SSOUTP) of the shift schedule (SS) to neutral. The methodology then returns or exits through bubble 906.

At diamond 902, if SLP 606 is not park or neutral, the methodology advances to diamond 908 and determines whether SLP 606 is reverse R by the signal from the sensors NS₁ and NS₂. If SLP 606 is reverse, the methodology then advances to block 910 and sets shift schedule to reverse. The methodology then returns or exits through bubble 906.

At diamond 908, if SLP 606 is not reverse, the methodology advances to block 912 concludes o determines that SLP 606 is equal to overdrive OD, drive D or low L. The methodology then advances to block 914 and selects two adjacent lines based on the present shift schedule and the shift schedule graphs shown in FIGS. 5B through 5D for a SLP 606 of overdrive OD, drive D or low L. The methodology advances to block 916 and scans these lines using a technique called "point slope" (PSLOPE), to be described under section heading "PSLOPE METHOD" (FIGS. 6A and 6B) which is a linear interpolation technique (N_(o) on X-axis and throttle angle on Y-axis). The methodology advances to diamond 918 and determines whether there is a new shift schedule to a coastdown shift, i.e. second to first gear from the SSOUTP (for a downshift) and throttle angle (for coast versus kick). If there is a new shift schedule to a coastdown shift, the methodology advances to block 920 and checks the gear ratios of the gear assembly 500 by performing speed calculations to avoid a "shock" from a power-plant reversal situation. A power-plant reversal situation or condition exists when the wheels of the vehicle drive the engine through the transmission during deceleration rather than the engine driving the transmission, in turn, driving the wheels. The methodology advances to diamond 922 and determines whether a power-plant reversal situation or condition exists. If a power-plant reversal condition exists, the methodology advances to block 924 and does not change the shift schedule. The methodology returns or exits through bubble 926.

At diamond 918, if there is not a new shift schedule to a coastdown shift, the methodology advances to block 928. Also, if a power-plant reversal condition does not exist at diamond 922, the methodology advances to block 928. At block 928, the methodology allows for a new shift schedule. The methodology then advances to block 930 and checks for diagnostic situations or conditions as previously described in conjunction with FIG. 4. The methodology advances to diamond 932 and determines whether a diagnostic situation or condition exists. If a diagnostic condition does not exist, the methodology advances to block 934 and allows the shift schedule to proceed or be changed to the new shift schedule. If the diagnostic condition does exist, the methodology advances to block 936 and does not change the shift schedule. The methodology advances from blocks 934 and 936 to bubble 938 and exits or returns.

PSLOPE METHOD

Referring to FIGS. 6A and 6B, the "point slope" (PSLOPE) routine of block 916 of FIG. 5A is shown. The PSLOPE method determines the throttle angle given output speed N_(o) by scanning the shift lines in FIGS. 5B through 5D stored as a table in the memory of the transmission controller 3010. At the start of the PSLOPE routine in bubble 1000 of FIG. 6A, the methodology advances to block 1002 and temporarily stores the value for X in the memory of the transmission controller 3010. The methodology then advances to diamond 1004 and determines whether X is less than or equal to X_(o) (FIG. 6B) which is a point on the shift line. If X is less than or equal to X_(o), the methodology advances to block 1006 and gets or obtains the value for Y_(o) and returns or exits through bubble 1008. If X is greater than X_(o), the methodology advances to diamond 1010 and determines whether X is less than X_(n). If X is less than X_(R), the methodology advances to block 1012 and computes the slope between the points X_(R) and X_(R-1) : The methodology then advances to block 1014 and computes Y based on Y_(R) plus slope. The methodology then returns or exits through bubble 1016.

At diamond 1010, if X is not less than X_(R), the methodology advances to diamond 1018 and determines whether the method is at the end of a table of values for the shift schedule graphs (FIGS. 5B-D), i.e. X_(o) ; Y_(o) ; X_(R) ; Y_(R) ; X_(n) ; Y_(n). If the method is not at the end of the table, the methodology advances to block 1020 and goes to the next row of the table. The methodology then loops back to diamond 1010.

If the methodology is at the end of the table at diamond 1018, the methodology advances to block 1022 and concludes or determines that the value for X is not in the table but greater than X_(n) (FIG. 6B), and gets the Y_(n) value, i.e. the last value Y_(n) from the data table based on the value for X_(n). The methodology then returns or exits through bubble 1016.

PRNODDL METHOD

The PRNODDL method is used to read sensors sensing the position of the manual lever 578 to determine the driver-selected operating mode or shift lever position 606, i.e. PRNODDL. Referring to FIG. 2, the manual shaft 591 is connected to the manual lever 578. Neutral start grounding contacts or contact switch sensors (NS₁ and NS₂) threadably engage the transmission case 102 and are in radial alignment with a pair of circumferentially spaced outwardly extending projections or metal areas 3084 (FIG. 7) when the shift lever position is park P. The metal areas 3084 extend through an insulator or cap member 578a made of plastic and disposed partially and circumferentially about the manual lever 578. The contact switch sensors NS₁ and NS₂ can only be grounded when they are in radial alignment with the metal areas 3084 on the manual lever 578. A further detailed description of the structure is found under the ELECTRONIC CONTROLLER FOR AN AUTOMATIC TRANSMISSION heading.

The gear selector or shift lever position (PRNODDL) is measured by the contact switch sensors NS₁ and NS₂. Reverse light contacts (RL₁ and Rl₂ in FIG. 7) are connected to the backup lights of the vehicle in a known manner. NS₁ can only be grounded in park P and neutral N. The contact switch sensors NS₁ and NS₂ cannot be grounded with RL contacts closed. As a result, the contact switch sensors NS₁ and NS₂ make electrical contact with the RL contacts when the manual lever 578 is in the reverse position. Hence, continuity to the backup lights can only exist in reverse R.

Referring to FIG. 7, the PRNODDL method is shown schematically. The manual lever 578 and cap member 578a act as a cam and the contact switch sensors NS₁ and NS₂ act as the follower NS₁ and NS₂ provide a binary zero input when the center terminal or spring loaded contact pin 3082 is grounded by contacting the metal areas 3084 on the manual lever in 578. RL₁ and RL₂ provide a zero whenever the manual lever 578 pushes spring loaded contact pin 3082 on the contact switch sensors NS₁ and NS₂ upward disconnecting two internal contacts 3088 of the contact switch sensors NS₁ and NS₂ with the RL contacts. For example, in P, NS₁, NS₂, and RL₁, RL₂ provide a zero input. The remaining inputs are shown in the table below:

    __________________________________________________________________________     P           R  N    OD    D   L                                                __________________________________________________________________________     NS.sub.1                                                                           0 0.sub. 1.sub. 1                                                                     1                                                                                1                                                                                0 0.sub. 1                                                                           1  1   1    1                                                                                 1                                          RL.sub.1                                                                           0 0.sub. 0.sub. 0                                                                     1                                                                                0                                                                                0 0.sub. 0                                                                           1  0   0    0                                                                                 0                                          NS.sub.2                                                                           0 1.sub. 1.sub. 1                                                                     1                                                                                1                                                                                1 1.sub. 1                                                                           1  1   1    1                                                                                 0                                          RL.sub.2                                                                           0 0.sub. 0.sub. 1                                                                     1                                                                                1                                                                                1 0.sub. 0                                                                           0  0   1    0                                                                                 0                                          CODE                                                                               P T.sub.1 T.sub.2 D                                                                  R  D                                                                               N  T.sub.1 T.sub.2                                                                   OD T.sub.2                                                                           D     T.sub.2                                                                          L                                            __________________________________________________________________________

The PRNODDL codes are verified by pressure switch data to be described herein. If the engine of the vehicle is running (N_(e) is less than 500 r.p.m.), the transmission controller 3010 checks its permanent memory to see if the PRNODDL code determined above corresponds with pressure switch data from the pressure switches 646, 648 and 650 (FIGS. 3A-L) at the last "Engine running" check ("PRNODDL OK"). If the data corresponds, the transmission controller 3010 displays a valid PRNODDL code. If data does not correspond, the transmission controller 3010 displays "?? " and reports "PRNODDL Failures--Engine Off" to permanent memory.

If the engine is running at or above a predetermined speed (N_(e) equal or greater than 500 r.p.m.), the transmission controller 3010 reads the PRNODDL code as above-described. If PRNODDL code is valid, the transmission controller 3010 verifies with the pressure switch data in the table below:

    ______________________________________                                         PRNODDL CODE/PRESSURE SWITCH                                                                          LR     2-4    OD                                        ______________________________________                                         PN             ON           OFF   OFF                                          R              OFF          OFF   OFF                                          OD, D, L       ON           ON    ON                                           ______________________________________                                    

SHIFT LEVER POSITION METHODOLOGY

The transmission control logic relies on the Shift Lever Position (SLP) methodology to identify the mode of transmission operation selected by the driver to provide hysteresis between the PRNODDL positions, and to permit limited operation of the transmission controller 3010 without functioning PRNODDL contact switch sensors (NS₁, NS₂, RL₁, RL₂) by utilizing pressure switch data from the pressure switches 646, 648 and 650 (FIGS. 3A-L) to identify the three hydraulic modes of operation (i.e. reverse R, neutral N and drive D). In the SLP methodology, P, R, N, and OD (overdrive) PRNODDL codes are accepted as being valid without regard to pressure switch data since the corresponding hydraulic porting (park and neutral are identical) condition must occur first. Testing for SLP position (checking pressure switch input) is only done with temporary or invalid codes present since this is the area where hydraulic porting changes occur.

Referring to FIGS. 8A and 8B, the shift lever position (SLP) methodology is shown. At the beginning in block 1800, the methodology advances to diamond 1802 and determines whether the PRNODDL code (PC) from the sensors (NS₁, NS₂, RL₁, RL₂) is equal to a code for park P, neutral N or a temporary code (T₁) stored in memory in the transmission controller 3010. If PC is equal to park, reverse or a temporary code, the methodology advances to block 1804 and sets the shift lever position (SLP) 606 (FIGS. 3A-3L) equal to neutral. If PC is not equal to park, neutral or a temporary code, the methodology advances to diamond 1806 and determines whether PC is equal to reverse R or overdrive OD. If PC equals reverse or overdrive, the methodology advances to block 1808 and sets the SLP 606 equal to PC. If PC is not equal to reverse or overdrive, the methodology advances to diamond 1810 and determines whether PC is in drive D or low L. If PC is drive or low, the methodology advances to diamond 1812 and determines whether SLP 606 is reverse or neutral. If SLP 606 is not reverse or neutral, the methodology advances to diamond 1813 and determines whether a neutral to first gear (N-1) shift is in progress by looking for a flag. If a neutral to first gear shift is not in progress, the methodology advances to block 1808 previously described and sets SLP 606 equal to PC.

If SLP 606 is reverse or neutral at diamond 1812, or PC does not equal drive or low at diamond 1810, or a neutral to first gear shift is in progress, the methodology advances to diamond 1814 and determines whether PC equals an invalid code (I) stored in memory. If PC is an invalid code, the methodology advances to diamond 1816 and determines whether a PRNODDL FAIL (PF) flag has been set. If PF has not been set, the methodology advances to block 1817 and determines whether a count n on a counter is greater than a predetermined value such as 15. If the count n is greater than the predetermined value, the methodology advances to block 1818 and sets PF. If the count n is not greater than the predetermined value, the methodology advances to block 1819 and increments the count n. The methodology then advances to diamond 1821. If PC is not an invalid code at diamond 1814, the methodology advances to block 1820 and sets the count n on the counter equal to a predetermined value such as zero. The methodology then advances to diamond 1821. If PF was previously set at diamond 1816 or once the PF flag has been set at diamond 1818, the methodology advances to diamond 1821 and determines whether SLP 606 is reverse. If SLP is reverse, the methodology advances to block 1822 and turns ON the low/reverse clutch solenoid-actuated valve 636. The methodology then advances to diamond 1823 and determines whether the low/reverse pressure switch 650 is equal to one or pressurized. If the low/reverse pressure switch 650 is equal to one, the methodology advances to block 1824 and sets SLP 606 equal to neutral. This occurs because the low/reverse pressure switch 650 is pressurized or producing a signal equal of one (See FIG. 3A) only when the transmission 100 is not in reverse gear and the low/reverse clutch 310 is being applied. If the low/reverse pressure switch 650 is not equal to one, the methodology advances to block 1837 to be described.

If SLP 606 is not reverse at diamond 1821, the methodology advances to diamond 1826 and determines whether SLP 606 is equal to neutral. If SLP is neutral, the methodology advances to block 1827 to set an SLP test flag. The methodology then advances to diamond 1828 and determines whether the overdrive pressure switch 646 is equal to one or pressurized. If the overdrive pressure switch 646 equals one, the methodology advances to block 1824 and sets a count Z on a counter equal to a predetermined value such as 43. The methodology then advances to block 1830 and sets SLP 606 equal to overdrive OD. This occurs because the overdrive clutch 304 is being applied when the overdrive pressure switch 646 is pressurized or producing a signal equal to one (See FIG. 3H). If the overdrive pressure switch 646 does not equal one, the methodology advances to diamond 1832 and determines whether the low/reverse solenoid-actuated valve 656 is ON, the pressure switches 646, 648 and 650 are not pressurized or are equal to zero (See FIG. 3C) and N_(o) is greater than a predetermined value, i.e. 500 r.p.m. If that criteria is true, the methodology advances to block 1834 and sets SLP 606 equal to reverse. If that criteria is not true, the methodology returns.

At diamond 1826, if SLP 606 is not neutral, the methodology advances to diamond 1836 and determines whether engine speed N_(e) is less than a predetermined speed, i.e. 500 r.p.m. If engine speed N_(o) is less than the predetermined speed, the methodology advances to block 1837 and decrements the count Z on the counter by a predetermined value. The methodology then advances to block 1838 and clears the SLP test flag. The methodology then returns. If engine speed N_(e) is not less than the predetermined speed, the methodology advances to diamond 1839 and determines whether a shift is in progress or occurring by looking for a flag. If the shift is in progress, the methodology advances to diamond 1840 and determines whether a neutral to first gear shift is in progress as previously described. If a neutral to first gear shift is not in progress, the methodology advances to block 1837 previously described. If the shift is not in progress, or a neutral to first gear shift is in progress, the methodology advances to diamond 1841 and determines whether the LU switch valve 614 is being applied as a result of the low/reverse element solenoid-actuated valve 636 being energized or on and low/reverse pressure switch 650 equals one and both the two/four 648 and overdrive 646 pressure switches equal zero. If that criteria is true, the methodology advances to block 1842 and sets SLP 606 equal to neutral. If that criteria is not true, the methodology advances to diamond 1843 and determines whether the transmission 100 is presently in fourth gear by calculating speeds. If the transmission 100 is presently is fourth gear, the methodology advances to diamond 1844 and determines whether the pressure switches 646, 648 and 650 equal zero. If the pressure switches equal zero, the methodology advances to block 1842 previously described. If all the pressure switches 646, 648 and 650 do not equal zero, the methodology advances to block 1837 previously described.

If the transmission 100 is not presently in fourth gear, the methodology advances to diamond 1845 and determines whether count Z equals a predetermined value such as zero. If Z does not equal zero, the methodology advances to block 1837 previously described. If Z equals zero, the methodology advances to diamond 1846 and determines whether the transmission 100 is presently in first gear by speed calculations, the low/reverse pressure switch 650 equals one and turbine speed N_(t) is greater than a predetermined r.p.m., or the pressure switches 646, 648 and 650 equal zero, or the low/reverse pressure switch 650 equals one and a neutral to first gear shift is in progress. If any of that criteria is not true, the methodology advances to diamond 1847 and determines whether the SLP test flag has been set. If the SLPT flag has not been set, the methodology advances to block 1837 previously described. If the SLP test flag has been set, the methodology advances to block 1848 and sets Z equal to a predetermined value such as 43. The methodology then advances to block 1838 previously described. If any of the criteria in diamond 1846 is true, the methodology advances to block 1849 and sets the SLP test flag and starts or continues a SLP timer (SLPT). The methodology then advances to diamond 1850 and determines whether the time on the SLPT timer is greater than a predetermined time period. If the time on the SLPT timer is not greater than the predetermined time period, the methodology returns. If the time on the SLPT timer is greater than the predetermined time period, the methodology advances to diamond 1851 and determines whether the transmission 100 is operating in first gear by performing speed calculations. If the transmission 100 is not operating in first gear, the methodology advances to block 1852 and sets SLP 606 equal to neutral. The methodology then advances to block 1838 previously described. If the transmission 100 is operating in first gear, the methodology advances to diamond 1854 and determines whether the low/reverse pressure switch 650 equals one. If the low/reverse pressure switch 650 does not equal one, the methodology advances to block 1856 and sets SLP 606 equal to reverse (See FIG. 3C). The methodology then advances to block 1838 previously described. If the low/reverse pressure switch 650 does equal one, the methodology advances to block 1852 and sets SLP 606 equal to neutral (See FIG. 3A). The methodology then advances to block 1838 previously described.

NEUTRAL START SWITCH TO SENSE SHIFT LEVER POSITION

Referring briefly now to FIG. 7, a diagrammatic representation of the operation of the sensors NS₁ /RL₁ and NS₂ /RL₁ is shown. Specifically, FIG. 7 shows that the sensors NS₁ /RL₁ and NS₂ /RL₂ are each provided with a spring loaded contact pin, such as pin 3082, which engages the cap member 578a of the manual lever 578. The cap member 578a is formed to permit metal areas of the manual lever 578 to extend through the cap member 578a, such as metal areas 3084. These metal areas 3084 are used to provide an electrical ground for the sensor. Thus, as shown in the corresponding table for the figure, each of the sensors NS₁ /RL₁ and NS₂ /RL₂ will produce a digital low or "θ" signal when their sensor or contact pin is in physical contact with one of the metal areas (e.g., metal area 3084). For example, in the park "P" position, both of the "NS" contacts of sensors NS₁ /RL₁ and NS₂ /RL.sub. 2 will be grounded, as shown by the corresponding columns of the table under section heading "PRNODDL METHOD".

The cap member 578a also includes non-grounded areas which are formed with trapezoidal shaped grooves, such as groove 3086. These grooves are used in connection with a set of internal contacts within the sensors NS₁ /RL₁ and NS₂ /RL₂ to create the four-bit digital code shown in the table for FIG. 7. These internal contacts 3088 are also illustrated in FIG. 7, which provides a schematic representation of one of the NS/RL sensors. When the contact pin 3082 of either of the sensors NS₁ /RL₁, NS₂ /RL₂ extends into one of the grooves 3086 of cap member 578a, then the internal "RL" contacts 3088 of that sensor will close and cause the sensor to produce a digital high or "1" signal from the electrical terminals of these contacts. As discussed previously, the internal contacts 3088 provide a set of reverse light "RL" contacts which are used in connection with the reverse or back-up lights of the vehicle.

In operation, actuation of the gear shift lever will cause a rotation of the manual lever 578 to the position selected by the vehicle operator. As the manual lever 578 rotates, the sensors NS₁ /RL₁ and NS₂ /RL₂ will produce a four-bit code which will correspond to the rotational position of the manual lever 578. The transmission controller 3010 will then determine the mode of operation selected through the four-bit code produced by the sensors NS₂ /RL₂ and NS₂ /NL₂.

Referring again to FIG. 9, the transmission controller 3010 receives input signals from the PRNODDL sensor block 3080, as well as produces output signals to a PRNODDL indicator contained in the passenger compartment. This PRNODDL indicator may, for example, be a suitable light source or other appropriate indicator for providing the operator with a visual indication of the operating mode which has been selected.

FIG. 9 also indicates that a pressure switch block 3090 is connected to the hydraulic controls block 3060. In connection with transmission 100, the pressure switch block 3090 would comprise the pressure switches 646, 648 and 650 (FIGS. 3A-L). As described above, each of these pressure switches is adapted to provide a signal indicative of a predetermined pressure level in the corresponding passageways leading to selected friction elements. Specifically, each of these pressure switches provide a digital input signal to the transmission controller 3010 which will indicate whether or not this pressure level has been reached.

FIG. 9 also indicates that the Transmission block includes a speed sensors block 3100 which is connected to the friction elements gear box 3070. In connection with the transmission 100, the speed sensors block 3100 comprises the input or turbine speed sensor 320 and the output speed sensor 546 which are both mounted to the transmission case 102. However, as previously indicated, other suitable speed sensor means may be provided either within or outside of the transmission case 102 in order to provide the desired input or turbine and output speed signals to the transmission controller 3010. The speed sensors block 3100 may also include a suitable engine speed sensor (e.g., hall effect device). However, if the engine controller 3020 is already receiving such a speed signal, then this signal could be shared with the transmission controller 3010 to avoid unnecessary duplication.

The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.

Obviously, many modifications and variations are possible in light of the above teachings. Therefore, the subject invention may be practiced otherwise than as specifically described. 

What is claimed is:
 1. A method of determining the manually drive-selected operating mode of a vehicle transmission by a plurality of contact switch sensors and a lever actuated in response to a manual input, said method comprising the steps of:actuating a lever to a predetermined position which is one of a plurality of driver-selected modes of the transmission; reading a plurality of contact switch sensors by a controller to determine whether the contact switch sensors are or are not grounded to the lever based on the predetermined position of the lever; reading a plurality of reverse contacts by the controller to determine whether the reverse contacts are opened or closed by the contact switch sensors; generating a binary code by the contact switch sensors and reverse contacts; and determining the driver-selecting operating mode of the transmission by the controller based on whether the contact switch sensors are or are not grounded and whether the reverse contacts are opened or closed.
 2. A method as set forth in claim 1 including the step of determining that the driver-selected operating mode is park when a plurality of neutral start sensors are grounded.
 3. A method as set forth in claim 1 including the step of determining that the driver-selected operating mode is reverse when the neutral start sensors are not grounded and a plurality of reverse contacts are closed.
 4. A method as set forth in claim 1 including the step of determining that the driver-selected operating mode is neutral when a first neutral start contact is grounded and a second reverse contact is closed.
 5. A method as set forth in claim 1 including the step of determining that the driver-selected operating mode is overdrive when the neutral start sensors are not grounded and a first reverse contact is closed.
 6. A method as set forth in claim 1 including the step of determining that the driver-selected operating mode is drive when the neutral start sensors are not grounded and the second reverse contact is closed.
 7. A method as set forth in claim 1 including the step of determining that the driver-selected operating mode is low when a second neutral start contact is grounded and the reverse contacts are open.
 8. A method of determining the manually driver-selected operating mode of a vehicle transmission by a manually actuated lever, said method comprising the steps of:manually actuating a lever to a predetermined position which is one of a plurality of driver-selected operating modes of the transmission; reading a first and second sensor by a controller to determine whether the sensors are grounded to the manually actuated lever; reading whether a first and second reverse contacts to determine whether the reverse contacts are closed by the sensors; generating a binary code by the sensors and reverse contacts; determining the driver-selected operating mode by the controller based on whether the first and second sensors are grounded and the first and second reverse contacts are closed; determining that the driver-selected operating mode is park when the first and second sensor are grounded; determining that the driver-selected operating mode is reverse when the first and second sensor are not grounded and the first and second reverse contacts are closed; determining that the driver-selected operating mode is neutral when the first sensor is grounded and the second reverse contact is closed; determining that the driver-selected operating mode is overdrive when the first and second sensor are not grounded and the first reverse contact is closed; determined that the driver-selected operating mode is low when the the first and second sensors are not grounded and the second reverse contact is closed; and determining that the driver-selected operating mode is low when the second sensor is grounded and the first and second reverse contacts are open. 